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Intel® Atom™ Processor D400 Series (Single Core) Specification Update December 2012 Revision 006 Document Number: 322861-006 INFORMATION IN THIS DOCUMENT IS PROVIDED IN CONNECTION WITH INTEL® PRODUCTS. NO LICENSE, EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS DOCUMENT. EXCEPT AS PROVIDED IN INTEL'S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, INTEL ASSUMES NO LIABILITY WHATSOEVER, AND INTEL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY, RELATING TO SALE AND/OR USE OF INTEL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT. UNLESS OTHERWISE AGREED IN WRITING BY INTEL, THE INTEL PRODUCTS ARE NOT DESIGNED NOR INTENDED FOR ANY APPLICATION IN WHICH THE FAILURE OF THE INTEL PRODUCT COULD CREATE A SITUATION WHERE PERSONAL INJURY OR DEATH MAY OCCUR. Intel may make changes to specifications and product descriptions at any time, without notice. Designers must not rely on the absence or characteristics of any features or instructions marked "reserved" or "undefined." Intel reserves these for future definition and shall have no responsibility whatsoever for conflicts or incompatibilities arising from future changes to them. The information here is subject to change without notice. Do not finalize a design with this information. Intel® Atom™ Processor D400 Series may contain design defects or errors known as errata which may cause the product to deviate from published specifications. Current characterized errata are available on request. Intel processor numbers are not a measure of performance. Processor numbers differentiate features within each processor family, not across different processor families. Over time processor numbers will increment based on changes in clock, speed, cache, FSB, or other features, and increments are not intended to represent proportional or quantitative increases in any particular feature. Current roadmap processor number progression is not necessarily representative of future roadmaps. See www.intel.com/products/processor_number for details. Contact your local Intel sales office or your distributor to obtain the latest specifications and before placing your product order. Intel, the Intel logo, Intel Pineview-D, and Intel Pineview-D Inside are trademarks of Intel Corporation in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Copyright © 2012, Intel Corporation. All rights reserved. 2 Specification Update Contents Preface ................................................................................................................................. 5 Identification Information ....................................................................................................... 7 Summary Tables of Changes ................................................................................................... 9 Errata.................................................................................................................................. 15 Specification Changes ........................................................................................................... 33 Specification Clarifications ..................................................................................................... 34 Documentation Changes ........................................................................................................ 35 Specification Update 3 Revision History Revision Revision Date Description 001 • Initial Release December 2009 002 • Errata update February 2010 003 • D425 SKU added June 2010 004 • AAR43 and AAR44 Errata added September 2010 005 • AAR45 and AAR46 Errata added January 2012 006 • AAR47 Erratum added December 2012 § 4 Specification Update Preface Preface This document is an update to the specifications contained in the documents listed in the following Affected Documents/Related Documents table. It is a compilation of device and document errata and specification clarifications and changes, and is intended for hardware system manufacturers and for software developers of applications, operating system, and tools. Information types defined in the Nomenclature section of this document are consolidated into this update document and are no longer published in other documents. This document may also contain information that has not been previously published. Affected Documents Document Title Document Number/ Location1 Intel® Atom™ Processor D400 and D500 Series Datasheet – Volume 1 and 2 322844-001, 322845-001 Intel® Atom™ Processor D400 and D500 Series Thermal Mechanical Design Guidelines 322856-001 Related Documents Document Title Document Number/ Location1 Intel® 64 and IA-32 Architectures Software Developer's Manual Documentation Changes 2520462 Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1: Basic Architecture 2536652 Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 2A: Instruction Set Reference, A-M 2536662 Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 2B: Instruction Set Reference, N-Z 2536672 Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3A: System Programming Guide 2536682 Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3B: System Programming Guide 2536692 IA-32 Intel® Architectures Optimization Reference Manual 2489662 ® Intel Processor Identification and the CPUID Instruction Application Note (AP-485) 2416182 Intel® 64 and IA-32 Architectures Application Note TLBs, PagingStructure Caches, and Their Invalidation 3170802 Specification Update 5 Preface Nomenclature Errata are design defects or errors. These may cause the processor behavior to deviate from published specifications. Hardware and software designed to be used with any given stepping must assume that all errata documented for that stepping are present on all devices. S-Spec Number is a five-digit code used to identify products. Products are differentiated by their unique characteristics, for example, core speed, L2 cache size, package type, etc. as described in the processor identification information table. Read all notes associated with each S-Spec number. Specification Changes are modifications to the current published specifications. These changes will be incorporated in any new release of the specification. Specification Clarifications describe a specification in greater detail or further highlight a specification’s impact to a complex design situation. These clarifications will be incorporated in any new release of the specification. Documentation Changes include typos, errors, or omissions from the current published specifications. These will be incorporated in any new release of the specification. Note: Errata remain in the specification update throughout the product’s lifecycle, or until a particular stepping is no longer commercially available. Under these circumstances, errata removed from the specification update are archived and available upon request. Specification changes, specification clarifications and documentation changes are removed from the specification update when the appropriate changes are made to the appropriate product specification or user documentation (datasheets, manuals, etc.). § 6 Specification Update Identification Information Identification Information Intel® Atom™ Processor D400 Series on 45-nm process stepping can be identified by the register contents in Table 1. When EAX is initialized to a value of 1, the CPUID instruction returns the Extended Family, Extended Model, Type, Family, Model and Stepping value in the EAX register. Note that the EDX processor signature value after reset is equivalent to the processor signature output value in the EAX register. Table 1. Component Identification via Programming Interface Reserved Extended Family1 Extended Model2 Reserved Processor Type3 Family Code4 Model Number5 Stepping ID6 31:28 27:20 19:16 15:13 12 11:8 7:4 3:0 0000000b 0001b 0b 0110b 1100b XXXXb NOTES: 1. The Extended Family, bits [27:20] are used in conjunction with the Family Code, specified in bits [11:8], to indicate whether the processor belongs to the Intel386®, Intel486®, Pentium®, Pentium Pro, Pentium 4, or Intel Core processor family. 2. The Extended Model, bits [19:16] in conjunction with the Model Number, specified in bits [7:4], are used to identify the model of the processor within the processor’s family. 3. The Processor Type, specified in bits [13:12] indicates whether the processor is an original OEM processor, an OverDrive processor, or a dual processor (capable of being used in a dual processor system). 4. The Family Code corresponds to bits [11:8] of the EDX register after RESET, bits [11:8] of the EAX register after the CPUID instruction is executed with a 1 in the EAX register, and the generation field of the Device ID register accessible through Boundary Scan. 5. The Model Number corresponds to bits [7:4] of the EDX register after RESET, bits [7:4] of the EAX register after the CPUID instruction is executed with a 1 in the EAX register, and the model field of the Device ID register accessible through Boundary Scan. 6. The Stepping ID in bits [3:0] indicates the revision number of that model. See Table 2 for the processor stepping ID number in the CPUID information. Specification Update 7 Identification Information Component Marking Information Intel Atom Processor D400 Series is identified by the following component markings. Figure 1. Intel Atom Processor D400 Series Markings SAMPLE MARKING INFORMATION: GRP1LINE1: INTEL{M}{C}08{e1} GRP2LINE1: {FPO} SSPEC PROC# Table 2. Identification Table for Desktop Intel Atom Processor D400 Series MCU QDF/ S-SPEC Number Product Stepping CPUID Max Core Speed Package Cache Size (KB) SLBMH A0 0x000106CAh 1.66 GHz MicroFCBGA8 512kB M01106CA107 SLBXD A0 0x000106CAh 1.80 GHz MicroFCBGA8 512kB M01106CA107 § 8 Specification Update Summary Tables of Changes Summary Tables of Changes The following table indicates the Specification Changes, Errata, Specification Clarifications or Documentation Changes, which apply to the listed processor steppings. Intel intends to fix some of the errata in a future stepping of the component, and to account for the other outstanding issues through documentation or Specification Changes as noted. This table uses the following notations: Codes Used in Summary Table Stepping X: Erratum, Specification Change or Clarification that applies to this stepping. Blank (No mark): This erratum is fixed in listed stepping or specification change does not apply to listed stepping. Doc: Document change or update that will be implemented. Plan Fix: This erratum may be fixed in a future stepping of the product. Fixed: This erratum has been previously fixed. No Fix: There are no plans to fix this erratum. Shaded: This item is either new or modified from the previous version of the document. Status Row Specification Update 9 Summary Tables of Changes Item Numbering Each Specification Update item is prefixed with a capital letter to distinguish the Product. The key below details the letters that are used in Intel’s microprocessor specification updates: A = Dual-Core Intel® Xeon® processor 7000 sequence C = Intel® Celeron® processor D = Dual-Core Intel® Xeon® processor 2.80 GHz E = Intel® Pentium® III processor F = Intel® Pentium® processor Extreme Edition and Intel® Pentium® D processor I = Dual-Core Intel® Xeon® processor 5000 series J = 64-bit Intel® Xeon® processor MP with 1-MB L2 Cache K = Mobile Intel® Pentium® III processor L = Intel® Celeron® D processor M = Mobile Intel® Celeron® processor N = Intel ® Pentium® 4 processor O = Intel ® Xeon® processor MP P = Intel ® Xeon® processor Q = Mobile Intel® Pentium® 4 processor supporting Hyper-Threading Technology on 90-nm process technology R = Intel® Pentium® 4 processor on 90 nm process S = 64-bit Intel® Xeon® processor with 800 MHz system bus (1 MB and 2 MB L2 cache versions) T = Mobile Intel® Pentium® 4 processor–M U = 64-bit Intel® Xeon® processor MP with up to 8MB L3 Cache V = Mobile Intel® Celeron® processor on .13 Micron Process in Micro-FCPGA Package W= Intel® Celeron®-M processor X = Intel® Pentium® M processor on 90-nm process with 2-MB L2 cache and Intel® Processors A100 and A110 with 512-KB L2 cache Y = Intel® Pentium® M processor Z = Mobile Intel® Pentium® 4 processor with 533 MHz system bus AA= Intel® Pentium® D Processor 900 Sequence and Intel® Pentium® processor Extreme Edition 955, 965 AB= Intel® Pentium® 4 processor 6x1 Sequence AC= Intel® Celeron® processor in 478 pin package AD = Intel® Celeron® D processor on 65 nm process AE = Intel® Core™ Duo processor and Intel® Core™ Solo processor on 65nm process AF = Dual-Core™ Intel® Xeon® processor LV AG = Dual-Core Intel® Xeon® processor 5100 Series AH= Intel® Core™2 Duo mobile processor AI = Intel® Core™2 Extreme processor X6800Δ and Intel® Core™2 Duo Desktop processor E6000 and E4000 Sequence 10 Specification Update Summary Tables of Changes AJ = Quad-Core Intel® Xeon® processor 5300 Series AK = Intel® Core™2 Extreme quad-core processor QX6700 and Intel® Core™2 Quad processor Q6600 AL = Dual-Core Intel® Xeon® processor 7100 Series AN = Intel® Pentium® Dual-Core processor AO = Quad-Core Intel® Xeon® processor 3200 Series AP = Dual-Core Intel® Xeon® processor 3000 Series AQ = Intel® Pentium® Dual-Core Desktop Processor E2000 Sequence AR = Intel® Celeron® Processor 500 Series AR = Intel® Celeron processor 500 series AS = Intel® Xeon® processor 7200, 7300 series AV = Intel® Core™2 Extreme processor QX9000 sequence and Intel® Core™2 Quad processor Q9000 sequence processor AW = Intel® Core™ 2 Duo AX =Quad-Core Intel® Xeon® processor 5400 series AY =Dual-Core Intel® Xeon® processor 5200 series AZ =Intel® Core™2 Duo processor and Intel® Core™2 Extreme processor on 45nm process AAE = Intel® Atom™ processor Z5xx series AAF = Intel® Atom™ processor 200 series AAG = Intel® Atom™ processor N280 series AAH = Intel® Atom™ processor 300 series AAR = Intel® Atom™ processor D400 series AAS = Intel® Atom™ processor N400 series AAV = Intel® Atom™ processor D500 series Note: Intel processor numbers are not a measure of performance. Processor numbers differentiate features within each processor family, not across different processor families. See http://www.intel.com/products/processor_number for details. Number Stepping PLAN ERRATA A0 AAR1 X No Fix An xTPR Update Transaction Cycle, if Enabled, May be Issued to the FSB after the Processor has Issued a Stop-Grant Special Cycle AAR2 X No Fix The Processor May Report a #TS Instead of a #GP Fault AAR3 X No Fix Writing the Local Vector Table (LVT) when an Interrupt is Pending May Cause an Unexpected Interrupt AAR4 X No Fix MOV To/From Debug Registers Causes Debug Exception AAR5 X No Fix A Write to an APIC Register Sometimes May Appear to Have Not Occurred AAR6 X No Fix Using 2M/4M Pages When A20M# Is Asserted May Result in Incorrect Address Translations Specification Update 11 Summary Tables of Changes Number Stepping PLAN ERRATA A0 AAR7 X No Fix Value for LBR/BTS/BTM will be Incorrect after an Exit from SMM AAR8 X No Fix Incorrect Address Computed For Last Byte of FXSAVE/FXRSTOR Image Leads to Partial Memory Update AAR9 X No Fix A Thermal Interrupt is Not Generated when the Current Temperature is Invalid AAR10 X No Fix Programming the Digital Thermal Sensor (DTS) Threshold May Cause Unexpected Thermal Interrupts AAR11 X No Fix Returning to Real Mode from SMM with EFLAGS.VM Set May Result in Unpredictable System Behavior AAR12 X No Fix Fault on ENTER Instruction May Result in Unexpected Value on Stack Frame AAR13 X No Fix With TF (Trap Flag) Asserted, FP Instruction That Triggers an Unmasked FP Exception May Take Single Step Trap before Retirement of Instruction AAR14 X No Fix An Enabled Debug Breakpoint or Single Step Trap May Be Taken after MOV SS/POP SS Instruction if it is Followed by an Instruction That Signals a Floating Point Exception AAR15 X No Fix Code Segment Limit/Canonical Faults on RSM May be Serviced before Higher Priority Interrupts/Exceptions and May Push the Wrong Address Onto the Stack AAR16 X No Fix BTS(Branch Trace Store) and PEBS(Precise Event Based Sampling) May Update Memory outside the BTS/PEBS Buffer AAR17 X No Fix Single Step Interrupts with Floating Point Exception Pending May Be Mishandled AAR18 X No Fix Unsynchronized Cross-Modifying Code Operations Can Cause Unexpected Instruction Execution Results AAR19 X No Fix A Page Fault May Not be Generated When the PS bit is set to “1” in a PML4E or PDPTE AAR20 X No Fix IO_SMI Indication in SMRAM State Save Area May be Set Incorrectly AAR21 X No Fix Writes to IA32_DEBUGCTL MSR May Fail when FREEZE_LBRS_ON_PMI is Set AAR22 X No Fix Address Reported by Machine-Check Architecture (MCA) on L2 Cache Errors May be Incorrect AAR23 X No Fix Performance Monitoring Event for Outstanding Bus Requests Ignores AnyThread Bit AAR24 X No Fix Corruption of CS Segment Register During RSM While Transitioning From Real Mode to Protected Mode AAR25 X No Fix GP and Fixed Performance Monitoring Counters With AnyThread Bit Set May Not Accurately Count Only OS or Only USR Events AAR26 X No Fix PMI Request is Not Generated on a Counter Overflow if Its OVF Bit is Already Set in IA32_PERF_GLOBAL_STATUS AAR27 X No Fix Processor May Use an Incorrect Translation if the TLBs Contain Two Different Translations For a Linear Address 12 Specification Update Summary Tables of Changes Number Stepping PLAN ERRATA A0 AAR28 X No Fix PEBS Record not Updated when in Probe Mode AAR29 X No Fix LBR/BTM/BTS Information Immediately After a Transition From Legacy/Compatibility Mode to 64-bit Mode May be Incorrect AAR30 X No Fix Pending x87 FPU Exceptions (#MF) Following STI May Be Serviced Before Higher Priority Interrupts AAR31 X No Fix Benign Exception after a Double Fault May Not Cause a Triple Fault Shutdown AAR32 X No Fix IA32_MC1_STATUS MSR Bit[60] Does Not Reflect Machine Check Error Reporting Enable Correctly AAR33 X No Fix LINT0 Assertion and Deassertion During an Inactive State May Cause Unexpected Operation When APIC is Disabled AAR34 X No Fix IRET under Certain Conditions May Cause an Unexpected Alignment Check Exception AAR35 X No Fix HSYNC and VSYNC Buffers Do Not Meet VESA Rise and Undershoot Specification AAR36 X No Fix Glitch on LVDS Display Interface Clocks and Data Lines May be Observed During Power Up Sequence AAR37 X No Fix CPUID Instruction Returns Incorrect Brand String AAR38 X No Fix IA32_MC2_STATUS [OVERFLOW] Bit is Not Set When Single-Bit Correctable ECC Error Occurs AAR39 X No Fix FP Data Operand Pointer May Be Incorrectly Calculated After an FP Access Which Wraps a 4-Gbyte Boundary in Code That Uses 32-Bit Address Size in 64-bit Mode AAR40 X No Fix Writes to Set IA32_MCG_STATUS.MCIP Will Fail AAR41 X No Fix Synchronous Reset of IA32_MPERF on IA32_APERF Overflow May Not Work AAR42 X No Fix During a C-State Exit due to a Pending External Interrupt the System May Hang AAR43 X No Fix High Temperature Circuit Marginality Issue May Cause the System to Hang or Auto Reboot AAR44 X No Fix FP Data Operand Pointer May Be Incorrectly Calculated After an FP Access Which Wraps a 64-Kbyte Boundary in 16-Bit Code AAR45 X No Fix Executing LTR in 64-bit Mode May Access Segment Descriptor Before Checking for Null Selector AAR46 X No Fix tREFI Exceeds DDR2 / DDR3 specifications AAR47 X No Fix Complex Conditions Associated With Instruction Page Remapping or Self/Cross-Modifying Code Execution May Lead to Unpredictable System Behavior Specification Update 13 Summary Tables of Changes Number Specification Changes There are no Specification Changes in this revision of the specification update Number Specification Clarifications There are no Specification Clarifications in this revision of the specification update Number Documentation Changes There are no Documentation Changes in this revision of the specification update § 14 Specification Update Errata Errata AAR1 An xTPR Update Transaction Cycle, if Enabled, May be Issued to the FSB after the Processor has Issued a Stop-Grant Special Cycle Problem: According to the FSB (Front Side Bus) protocol specification, no FSB cycles should be issued by the processor once a Stop-Grant special cycle has been issued to the bus. If xTPR update transactions are enabled by clearing the IA32_MISC_ENABLES[bit-23] at the time of Stop-Clock assertion, an xTPR update transaction cycle may be issued to the FSB after the processor has issued a Stop Grant Acknowledge transaction. Implication: When this erratum occurs in systems using C-states C2 (Stop-Grant State) and higher the result could be a system hang. Workaround: BIOS must leave the xTPR update transactions disabled (default). Status: For the steppings affected, see the Summary Tables of Changes. AAR2 Processor May Report a #TS Instead of a #GP Fault Problem: During system reset, there is insufficient time for handshake between ICH and GMCH LVDS logic. As a result, timing from panel backlight enable going low to LVDS data going low (TX) and timing from LVDS data going low to panel VCC enable going low (T3) do not match the programmed values. Panel backlight enable (LBKLT_EN), panel Vcc enable (LVDD_EN) and LVDS data lines go low at the same time. Implication: A jump to a busy TSS (Task-State Segment) may cause a #TS (invalid TSS exception) instead of a #GP fault (general protection exception). Workaround: None. Status: For the steppings affected, see the Summary Tables of Changes. AAR3 Writing the Local Vector Table (LVT) when an Interrupt is Pending May Cause an Unexpected Interrupt Problem: If a local interrupt is pending when the LVT entry is written, an interrupt may be taken on the new interrupt vector even if the mask bit is set. Implication: An interrupt may immediately be generated with the new vector when a LVT entry is written, even if the new LVT entry has the mask bit set. If there is no Interrupt Service Routine (ISR) set up for that vector the system will GP fault. If the ISR does not do an End of Interrupt (EOI) the bit for the vector is left set in the in-service register and mask all interrupts at the same or lower priority. Workaround: Any vector programmed into an LVT entry must have an ISR associated with it, even if that vector was programmed as masked. This ISR routine must do an EOI to clear any unexpected interrupts that may occur. The ISR associated with the spurious vector does not generate an EOI; therefore the spurious vector should not be used when writing the LVT. Status: For the steppings affected, see the Summary Tables of Changes. Specification Update 15 Errata AAR4 MOV To/From Debug Registers Causes Debug Exception Problem: When in V86 mode, if a MOV instruction is executed to/from a debug registers, a general-protection exception (#GP) should be generated. However, in the case when the general detect enable flag (GD) bit is set, the observed behavior is that a debug exception (#DB) is generated instead. Implication: With debug-register protection enabled (i.e., the GD bit set), when attempting to execute a MOV on debug registers in V86 mode, a debug exception is generated instead of the expected general-protection fault. Workaround: In general, operating systems do not set the GD bit when they are in V86 mode. The GD bit is generally set and used by debuggers. The debug exception handler should check that the exception did not occur in V86 mode before continuing. If the exception did occur in V86 mode, the exception may be directed to the general-protection exception handler. Status: For the steppings affected, see the Summary Tables of Changes. AAR5 A Write to an APIC Register Sometimes May Appear to Have Not Occurred Problem: With respect to the retirement of instructions, stores to the uncacheable memory based APIC register space are handled in a non-synchronized way. For example if an instruction that masks the interrupt flag, for example CLI, is executed soon after an uncacheable write to the Task Priority Register (TPR) that lowers the APIC priority, the interrupt masking operation may take effect before the actual priority has been lowered. This may cause interrupts whose priority is lower than the initial TPR, but higher than the final TPR, to not be serviced until the interrupt enabled flag is finally set, i.e. by STI instruction. Interrupts will remain pending and are not lost. Implication: In this example the processor may allow interrupts to be accepted but may delay their service. Workaround: This non-synchronization can be avoided by issuing an APIC register read after the APIC register write. This will force the store to the APIC register before any subsequent instructions are executed. No commercial operating system is known to be impacted by this erratum. Status: 16 For the steppings affected, see the Summary Tables of Changes. Specification Update Errata AAR6 Using 2M/4M Pages When A20M# Is Asserted May Result in Incorrect Address Translations Problem: An external A20M# pin if enabled forces address bit-20 to be masked (forced to zero) to emulates real-address mode address wraparound at 1 megabyte. However, if all of the following conditions are met, address bit-20 may not be masked. • paging is enabled • a linear address has bit-20 set • the address references a large page • A20M# is enabled Implication: When A20M# is enabled and an address references a large page the resulting translated physical address may be incorrect. This erratum has not been observed with any commercially available operating system. Workaround: Operating systems should not allow A20M# to be enabled if the masking of address bit-20 could be applied to an address that references a large page. A20M# is normally only used with the first megabyte of memory. Status: For the steppings affected, see the Summary Tables of Changes. AAR7 Value for LBR/BTS/BTM will be Incorrect after an Exit from SMM Problem: After a return from SMM (System Management Mode), the CPU will incorrectly update the LBR (Last Branch Record) and the BTS (Branch Trace Store), hence rendering their data invalid. The corresponding data if sent out as a BTM on the system bus will also be incorrect. Note: This issue would only occur when one of the 3 above mentioned debug support facilities are used. Implication: The value of the LBR, BTS, and BTM immediately after an RSM operation should not be used. Workaround: None. Status: For the steppings affected, see the Summary Tables of Changes. AAR8 Incorrect Address Computed For Last Byte of FXSAVE/FXRSTOR Image Leads to Partial Memory Update Problem: A partial memory state save of the 512-byte FXSAVE image or a partial memory state restore of the FXRSTOR image may occur if a memory address exceeds the 64KB limit while the processor is operating in 16-bit mode or if a memory address exceeds the 4GB limit while the processor is operating in 32-bit mode. Implication: FXSAVE/FXRSTOR will incur a #GP fault due to the memory limit violation as expected but the memory state may be only partially saved or restored. Workaround: Software should avoid memory accesses that wrap around the respective 16-bit and 32-bit mode memory limits. Status: For the steppings affected, see the Summary Tables of Changes. Specification Update 17 Errata AAR9 A Thermal Interrupt is Not Generated when the Current Temperature is Invalid Problem: When the DTS (Digital Thermal Sensor) crosses one of its programmed thresholds it generates an interrupt and logs the event (IA32_THERM_STATUS MSR (019Ch) bits [9,7]). Due to this erratum, if the DTS reaches an invalid temperature (as indicated IA32_THERM_STATUS MSR bit[31]) it does not generate an interrupt even if one of the programmed thresholds is crossed and the corresponding log bits become set. Implication: When the temperature reaches an invalid temperature the CPU does not generate a Thermal interrupt even if a programmed threshold is crossed. Workaround: None. Status: For the steppings affected, see the Summary Tables of Changes. AAR10 Programming the Digital Thermal Sensor (DTS) Threshold May Cause Unexpected Thermal Interrupts Problem: Software can enable DTS thermal interrupts by programming the thermal threshold and setting the respective thermal interrupt enable bit. When programming DTS value, the previous DTS threshold may be crossed. This will generate an unexpected thermal interrupt. Implication: Software may observe an unexpected thermal interrupt occur after reprogramming the thermal threshold. Workaround: In the ACPI/OS implement a workaround by temporarily disabling the DTS threshold interrupt before updating the DTS threshold value. Status: For the steppings affected, see the Summary Tables of Changes. AAR11 Returning to Real Mode from SMM with EFLAGS.VM Set May Result in Unpredictable System Behavior Problem: Returning back from SMM mode into real mode while EFLAGS.VM is set in SMRAM may result in unpredictable system behavior. Implication: If SMM software changes the value of the EFLAGS.VM in SMRAM, it may result in unpredictable system behavior. Intel has not observed this behavior in commercially available software. Workaround: SMM software should not change the value of EFLAGS.VM in SMRAM. Status: 18 For the steppings affected, see the Summary Tables of Changes. Specification Update Errata AAR12 Fault on ENTER Instruction May Result in Unexpected Value on Stack Frame Problem: The ENTER instruction is used to create a procedure stack frame. Due to this erratum, if execution of the ENTER instruction results in a fault, the dynamic storage area of the resultant stack frame may contain unexpected value (i.e. residual stack data as a result of processing the fault). Implication: Data in the created stack frame may be altered following a fault on the ENTER instruction. Please refer to "Procedure Calls For Block-Structured Languages" in IA-32 Intel® Architecture Software Developer’s Manual, Vol. 1, Basic Architecture, for information on the usage of the ENTER instructions. This erratum is not expected to occur in ring 3. Faults are usually processed in ring 0 and stack switch occurs when transferring to ring 0. Intel has not observed this erratum on any commercially available software. Workaround: None. Status: For the steppings affected, see the Summary Tables of Changes. AAR13 With TF (Trap Flag) Asserted, FP Instruction That Triggers an Unmasked FP Exception May Take Single Step Trap before Retirement of Instruction Problem: If an FP instruction generates an unmasked exception with the EFLAGS.TF=1, it is possible for external events to occur, including a transition to a lower power state. When resuming from the lower power state, it may be possible to take the single step trap before the execution of the original FP instruction completes. Implication: A Single Step trap is taken when not expected. Workaround: None. Status: For the steppings affected, see the Summary Tables of Changes. Specification Update 19 Errata AAR14 An Enabled Debug Breakpoint or Single Step Trap May Be Taken after MOV SS/POP SS Instruction if it is Followed by an Instruction That Signals a Floating Point Exception Problem: A MOV SS/POP SS instruction should inhibit all interrupts including debug breakpoints until after execution of the following instruction. This is intended to allow the sequential execution of MOV SS/POP SS and MOV [r/e]SP, [r/e]BP instructions without having an invalid stack during interrupt handling. However, an enabled debug breakpoint or single step trap may be taken after MOV SS/POP SS if this instruction is followed by an instruction that signals a floating point exception rather than a MOV [r/e]SP, [r/e]BP instruction. This results in a debug exception being signaled on an unexpected instruction boundary since the MOV SS/POP SS and the following instruction should be executed atomically. Implication: This can result in incorrect signaling of a debug exception and possibly a mismatched Stack Segment and Stack Pointer. If MOV SS/POP SS is not followed by a MOV [r/e]SP, [r/e]BP, there may be a mismatched Stack Segment and Stack Pointer on any exception. Intel has not observed this erratum with any commercially available software, or system. Workaround: As recommended in the IA32 Intel® Architecture Software Developer’s Manual, the use of MOV SS/POP SS in conjunction with MOV [r/e]SP, [r/e]BP will avoid the failure since the MOV [r/e]SP, [r/e]BP will not generate a floating point exception. Developers of debug tools should be aware of the potential incorrect debug event signaling created by this erratum. Status: For the steppings affected, see the Summary Tables of Changes. AAR15 Code Segment Limit/Canonical Faults on RSM May be Serviced before Higher Priority Interrupts/Exceptions and May Push the Wrong Address Onto the Stack Problem: Normally, when the processor encounters a Segment Limit or Canonical Fault due to code execution, a #GP (General Protection Exception) fault is generated after all higher priority Interrupts and exceptions are serviced. Due to this erratum, if RSM (Resume from System Management Mode) returns to execution flow that results in a Code Segment Limit or Canonical Fault, the #GP fault may be serviced before a higher priority Interrupt or Exception (for example NMI (Non-Maskable Interrupt), Debug break(#DB), Machine Check (#MC), etc.). If the RSM attempts to return to a noncanonical address, the address pushed onto the stack for this #GP fault may not match the non-canonical address that caused the fault. Implication: Operating systems may observe a #GP fault being serviced before higher priority Interrupts and Exceptions. Intel has not observed this erratum on any commercially available software. Workaround: None. Status: 20 For the steppings affected, see the Summary Tables of Changes. Specification Update Errata AAR16 BTS(Branch Trace Store) and PEBS(Precise Event Based Sampling) May Update Memory outside the BTS/PEBS Buffer Problem: If the BTS/PEBS buffer is defined such that: • The difference between BTS/PEBS buffer base and BTS/PEBS absolute maximum is not an integer multiple of the corresponding record sizes • BTS/PEBS absolute maximum is less than a record size from the end of the virtual address space • The record that would cross BTS/PEBS absolute maximum will also continue past the end of the virtual address space A BTS/PEBS record can be written that will wrap at the 4G boundary (IA32) or 264 boundary (EM64T mode), and write memory outside of the BTS/PEBS buffer. 64 Implication: Software that uses BTS/PEBS near the 4G boundary (IA32) or 2 boundary (EM64T mode), and defines the buffer such that it does not hold an integer multiple of records can update memory outside the BTS/PEBS buffer. Workaround: Define BTS/PEBS buffer such that BTS/PEBS absolute maximum minus BTS/PEBS buffer base is integer multiple of the corresponding record sizes as recommended in the IA-32 Intel® Architecture Software Developer’s Manual, Volume 3. Status: For the steppings affected, see the Summary Tables of Changes. AAR17 Single Step Interrupts with Floating Point Exception Pending May Be Mishandled Problem: In certain circumstances, when a floating point exception (#MF) is pending during single-step execution, processing of the single-step debug exception (#DB) may be mishandled. Implication: When this erratum occurs, #DB is incorrectly handled as follows: • #DB is signaled before the pending higher priority #MF (Interrupt 16) • #DB is generated twice on the same instruction Workaround: None. Status: For the steppings affected, see the Summary Tables of Changes. Specification Update 21 Errata AAR18 Unsynchronized Cross-Modifying Code Operations Can Cause Unexpected Instruction Execution Results Problem: The act of one processor, or system bus master, writing data into a currently executing code segment of a second processor with the intent of having the second processor execute that data as code is called cross-modifying code (XMC). XMC that does not force the second processor to execute a synchronizing instruction, prior to execution of the new code, is called unsynchronized XMC. Software using unsynchronized XMC to modify the instruction byte stream of a processor can see unexpected or unpredictable execution behavior from the processor that is executing the modified code. Implication: In this case, the phrase "unexpected or unpredictable execution behavior" encompasses the generation of most of the exceptions listed in the Intel Architecture Software Developer's Manual Volume 3A: System Programming Guide, including a General Protection Fault (#GP) or other unexpected behaviors. Workaround: In order to avoid this erratum, programmers should use the XMC synchronization algorithm as detailed in the Intel Architecture Software Developer's Manual Volume 3A: System Programming Guide, Section: Handling Self- and Cross-Modifying Code. Status: For the steppings affected, see the Summary Tables of Changes. AAR19 A Page Fault May Not be Generated When the PS bit is set to “1” in a PML4E or PDPTE Problem: On processors supporting Intel® 64 architecture, the PS bit (Page Size, bit 7) is reserved in PML4Es and PDPTEs. If the translation of the linear address of a memory access encounters a PML4E or a PDPTE with PS set to 1, a page fault should occur. Due to this erratum, PS of such an entry is ignored and no page fault will occur due to its being set. Implication: Software may not operate properly if it relies on the processor to deliver page faults when reserved bits are set in paging-structure entries. Workaround: Software should not set bit 7 in any PML4E or PDPTE that has Present Bit (Bit 0) set to “1”. Status: 22 For the steppings affected, see the Summary Tables of Changes. Specification Update Errata AAR20 IO_SMI Indication in SMRAM State Save Area May be Set Incorrectly Problem: The IO_SMI bit in SMRAM’s location 7FA4H is set to "1" by the CPU to indicate a System Management Interrupt (SMI) occurred as the result of executing an instruction that reads from an I/O port. Due to this erratum, the IO_SMI bit may be incorrectly set by: • A SMI that is pending while a lower priority event is executing • A REP I/O read • A I/O read that redirects to MWAIT Implication: SMM handlers may get false IO_SMI indication. Workaround: The SMM handler has to evaluate the saved context to determine if the SMI was triggered by an instruction that read from an I/O port. The SMM handler must not restart an I/O instruction if the platform has not been configured to generate a synchronous SMI for the recorded I/O port address. Status: For the steppings affected, see the Summary Tables of Changes. AAR21 Writes to IA32_DEBUGCTL MSR May Fail when FREEZE_LBRS_ON_PMI is Set Problem: When the FREEZE_LBRS_ON_PMI, IA32_DEBUGCTL MSR (1D9H) bit [11], is set, future writes to IA32_DEBUGCTL MSR may not occur in certain rare corner cases. Writes to this register by software or during certain processor operations are affected. Implication: Under certain circumstances, the IA32_DEBUGCTL MSR value may not be updated properly and will retain the old value. Intel has not observed this erratum with any commercially available software. Workaround: Do not set the FREEZE_LBRS_ON_PMI bit of IA32_DEBUGCTL MSR. Status: For the steppings affected, see the Summary Tables of Changes. AAR22 Address Reported by Machine-Check Architecture (MCA) on L2 Cache Errors May be Incorrect Problem: When an L2 Cache error occurs (Error code 0x010A or 0x110A reported in IA32_MCi_STATUS MSR bits [15:0]), the address is logged in the MCA address register (IA32_MCi_ADDR MSR). Under some scenarios, the address reported may be incorrect. Implication: Software should not rely on the value reported in IA32_MCi_ADDR MSR for L2 Cache errors. Workaround: None. Status: For the steppings affected, see the Summary Tables of Changes. Specification Update 23 Errata AAR23 Performance Monitoring Event for Outstanding Bus Requests Ignores AnyThread Bit Problem: The Performance Monitoring Event of Outstanding Bus Requests will ignore the AnyThread bit (IA32_PERFEVTSEL0 MSR (186H)/ IA32_PERFEVTSEL1 MSR (187H) bit [21]) and will instead always count all transactions across all logical processors, even when AnyThread is clear. Implication: The performance monitor count may be incorrect when counting only the current logical processor’s outstanding bus requests on a processor supporting HyperThreading Technology. Workaround: None identified. Status: For the steppings affected, see the Summary Tables of Changes. AAR24 Corruption of CS Segment Register During RSM While Transitioning From Real Mode to Protected Mode Problem: During the transition from real mode to protected mode, if an SMI (System Management Interrupt) occurs between the MOV to CR0 that sets PE (Protection Enable, bit 0) and the first far JMP, the subsequent RSM (Resume from System Management Mode) may cause the lower two bits of CS segment register to be corrupted. Implication: The corruption of the bottom two bits of the CS segment register will have no impact unless software explicitly examines the CS segment register between enabling protected mode and the first far JMP. Intel® 64 and IA-32 Architectures Software Developer’s Manual Volume 3A: System Programming Guide, Part 1, in the section titled "Switching to Protected Mode" recommends the far JMP immediately follows the write to CR0 to enable protected mode. Intel has not observed this erratum with any commercially available software. Workaround: None identified. Status: For the steppings affected, see the Summary Tables of Changes. AAR25 GP and Fixed Performance Monitoring Counters With AnyThread Bit Set May Not Accurately Count Only OS or Only USR Events Problem: A fixed or GP (general purpose) performance counter with the AnyThread bit (IA32_FIXED_CTR_CTRL_MSR (38DH) bit[2] for IA32_FIXED_CTR0, bit[6] for IA32_FIXED_CTR1, bit [10] for IA32_FIXED_CTR2; IA32_PERFEVTSEL0 MSR (186H)/ IA32_PERFEVTSEL1 MSR (187H) bit [21]) set may not count correctly when counting only OS (ring 0) events or only USR (ring>0) events. The counters will count correctly if they are counting both OS and USR events or if the AnyThread bit is clear. Implication: A performance monitor counter may be incorrect when it is counting for all logical processors on that core and not counting at all privilege levels. This erratum will only occur on processors supporting multiple logical processors per core. Workaround: None identified. Status: 24 For the steppings affected, see the Summary Tables of Changes. Specification Update Errata AAR26 PMI Request is Not Generated on a Counter Overflow if its OVF Bit is Already Set in IA32_PERF_GLOBAL_STATUS Problem: If a performance counter overflows and software does not clear the corresponding OVF (overflow) bit in IA32_PERF_GLOBAL_STATUS MSR (38Eh) then future overflows of that counter will not trigger PMI (Performance Monitoring Interrupt) requests. Implication: If software does not clear the OVF bit corresponding to a performance counter then future counter overflows may not cause PMI requests. Workaround: Software should clear the IA32_PERF_GLOBAL_STATUS.OVF bit in the PMI handler. Status: For the steppings affected, see the Summary Tables of Changes. AAR27 Processor May Use an Incorrect Translation if the TLBs Contain Two Different Translations For a Linear Address Problem: The TLBs may contain both ordinary and large-page translations for a 4-KByte range of linear addresses. This may occur if software modifies a PDE (page-directory entry) that is marked present to set the PS bit (this changes the page size used for the address range). If the two translations differ with respect to page frame, permissions, or memory type, the processor may use a page frame, permissions, or memory type that corresponds to neither translation. Implication: Due to this erratum, software may not function properly if it sets the PS flag in a PDE and also changes the page frame, permissions, or memory type for the linear addresses mapped through that PDE. Workaround: Software can avoid this problem by ensuring that the TLBs never contain both ordinary and large-page translations for a linear address that differ with respect to page frame, permissions, or memory type. Status: For the steppings affected, see the Summary Tables of Changes. AAR28 PEBS Record not Updated When in Probe Mode Problem: When a performance monitoring counter is configured for PEBS (Precise Event Based Sampling), overflows of the counter can result in storage of a PEBS record in the PEBS buffer. Due to this erratum, if the overflow occurs during probe mode, it may be ignored and a new PEBS record may not be added to the PEBS buffer. Implication: Due to this erratum, the PEBS buffer may not be updated by overflows that occur during probe mode. Workaround: None. Status: For the steppings affected, see the Summary Tables of Changes. Specification Update 25 Errata AAR29 LBR/BTM/BTS Information Immediately After a Transition From Legacy/Compatibility Mode to 64-bit Mode May be Incorrect Problem: If a transition from legacy/compatibility mode to 64-bit mode occurs and another branch event occurs before the first instruction executes (for example an external interrupt or trap) then any FROM address recorded by LBR (Last Branch Record), BTM (Branch Trace Message) or BTS (Branch Trace Store) on that second event may incorrectly report the upper 32-bits as zero. Implication: Due to this erratum, bits 63:32 of the ‘FROM’ value for LBR/BTM/BTS may be improperly zeroed after a transition to 64 bite mode when the RIP (Instruction Pointer Register) is greater than 4 Gigabyte. Workaround: None identified. This erratum may be detected by a ‘FROM’ address having its upper 32-bits zero but its lower 32-bits matching the previous ‘TO’ address recorded. Status: For the steppings affected, see the Summary Tables of Changes. AAR30 Pending x87 FPU Exceptions (#MF) Following STI May Be Serviced Before Higher Priority Interrupts Problem: Interrupts that are pending prior to the execution of the STI (Set Interrupt Flag) instruction are normally serviced immediately after the instruction following the STI. An exception to this is if the following instruction triggers a #MF. In this situation, the interrupt should be serviced before the #MF. Because of this erratum, if following STI, an instruction that triggers a #MF is executed while STPCLK#, Enhanced Intel SpeedStep Technology transitions or Thermal Monitor events occur, the pending #MF may be serviced before higher priority interrupts. Implication: Software may observe #MF being serviced before higher priority interrupts. Workaround: None identified. Status: For the steppings affected, see the Summary Tables of Changes. AAR31 Benign Exception after a Double Fault May Not Cause a Triple Fault Shutdown Problem: According to the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3A, “Exception and Interrupt Reference”, if another exception occurs while attempting to call the double-fault handler, the processor enters shutdown mode. Due to this erratum, any benign faults while attempting to call double-fault handler will not cause a shutdown. However Contributory Exceptions and Page Faults will continue to cause a triple fault shutdown. Implication: If a benign exception occurs while attempting to call the double-fault handler, the processor may hang or may handle the benign exception. Intel has not observed this erratum with any commercially available software. Workaround: None identified. Status: 26 For the steppings affected, see the Summary Tables of Changes. Specification Update Errata AAR32 IA32_MC1_STATUS MSR Bit[60] Does Not Reflect Machine Check Error Reporting Enable Correctly Problem: IA32_MC1_STATUS MSR (405H) bit[60] (EN- Error Enabled) is supposed to indicate whether the enable bit in the IA32_MC1_CTL MSR (404H) was set at the time of the last update to the IA32_MC1_STATUS MSR. Due to this erratum, IA32_MC1_STATUS MSR bit[60] instead reports the current value of the IA32_MC1_CTL MSR enable bit. Implication: IA32_MC1_STATUS MSR bit [60] may not reflect the correct state of the enable bit in the IA32_MC1_CTL MSR at the time of the last update. Workaround: None identified. Status: For the steppings affected, see the Summary Tables of Changes. AAR33 LINT0 Assertion and De-assertion During an Inactive State May Cause Unexpected Operation When APIC is Disabled Problem: An interrupt delivered via LINT0 pins when the APIC is hardware disabled (IA32_APIC_BASE MSR (1BH) bit [11] is cleared) will usually keep the pin asserted until after the interrupt is acknowledged. However, if LINT0 is asserted and then deasserted before the interrupt is acknowledged and both of the following are true: • The APIC is hardware disabled (IA32_APIC_BASE MSR bit [11] is clear) and • The processor is in an inactive state that was requested by MWAIT, I/O redirection, VM-entry or RSM, then the processor may operate incorrectly Implication: Due to this erratum, the processor may run unexpected code and/or generate an unexpected exception. Intel has not observed this erratum with any commercially available software. Workaround: If LINT0 is used, it is recommended to either leave the APIC enabled (IA32_APIC_BASE MSR bit [11] set to 1) or do not use MWAIT, I/O redirection, VMentry or RSM to enter an inactive state. Status: For the steppings affected, see the Summary Tables of Changes. AAR34 IRET under Certain Conditions May Cause an Unexpected Alignment Check Exception Problem: In IA-32e mode, it is possible to get an Alignment Check Exception (#AC) on the IRET instruction even though alignment checks were disabled at the start of the IRET. This can only occur if the IRET instruction is returning from CPL3 code to CPL3 code. IRETs from CPL0/1/2 are not affected. This erratum can occur if the EFLAGS value on the stack has the AC flag set, and the interrupt handler's stack is misaligned. In IA-32e mode, RSP is aligned to a 16-byte boundary before pushing the stack frame. Implication: In IA-32e mode, under the conditions given above, an IRET can get a #AC even if alignment checks are disabled at the start of the IRET. This erratum can only be observed with a software generated stack frame. Workaround: Software should not generate misaligned stack frames for use with IRET. Status: For the steppings affected, see the Summary Tables of Changes. Specification Update 27 Errata AAR35 HSYNC/VSYNC Buffer Does Not Meet VESA Rise & Undershoot Specification Problem: Both HSYNC (horizontal Sync) and VSYNC (vertical sync) signals are violating VESA (Video Electronics Standards Association) specification due to non-monotonic slow rise time on both signals. Implication: HSYNC and VSYNC signals may not meet VESA specification. Workaround: Insert a buffer in the HSYNC/VSYNC signal path before the video connector. Refer to Platform Design Guide and Customer Reference Board (CRB) schematic for reference. Status: For the steppings affected, see the Summary Tables of Changes. AAR36 Glitch on LVDS Display Interface Clocks and Data Lines May be Observed during Power-Up Sequences Problem: During power up sequence (transition to S0 state from G3, S3, S4 or S5 states) when LVDS (Low Voltage Differential Signal) power supply (1.8V source) ramps up, a glitch on LVDS clocks (LVD_A_CLKP, LVD_A_CLKN) and data lines (LVD_A_DAPAP[2:0], LVD_A_DATAN[2:0]) may be observed. Implication: Due to this erratum, a glitch may be seen during power up sequence. The glitch is not seen once the LVDS power supply is stable. Workaround: None identified. Status: For the steppings affected, see the Summary Tables of Changes. AAR37 CPUID Instruction Returns Incorrect Brand String Problem: When the CPUID instructions is executed with EAX = 80000002H, 80000003H and 80000004H, the returned brand string may be incorrect. The model number in the brand string may be prefixed with a “K” instead of the expected “D”. Implication: When this erratum occurs, the processor will report an incorrect model number in the brand string. Workaround: It is possible for the BIOS to contain a workaround for this erratum. Status: 28 For the steppings affected, see the Summary Tables of Changes. Specification Update Errata AAR38 IA32_MC2_STATUS [OVERFLOW] Bit is Not Set When Single-Bit Correctable ECC Error Occurs Problem: The OVERFLOW bit should be set if the VAL bit (IA32_MC2_STATUS (409H) bit [63]) is set when a new error occurs. Due to this erratum, the OVERFLOW bit (IA32_MC2_STATUS (409H) bit [62]) is only set when a prior uncorrected error (as indicated by the UC bit (IA32_MC2_STATUS (409H) bit [61])) is present at the time the second error occurs. Implication: Any L2 correctable error will not set the IA32_MC2_STATUS.OVERFLOW bit when overwriting a prior L2 correctable error. Workaround: The frequency of occurrence of this problem is reduced greatly if an operating system regularly polls and clears the machine check banks as this reduces the likelihood of an overflow condition. Status: For the steppings affected, see the Summary Tables of Changes. AAR39 FP Data Operand Pointer May Be Incorrectly Calculated After an FP Access Which Wraps a 4-Gbyte Boundary in Code That Uses 32-Bit Address Size in 64-bit Mode Problem: The FP (Floating Point) Data Operand Pointer is the effective address of the operand associated with the last non-control FP instruction executed by the processor. If an 80-bit FP access (load or store) uses a 32-bit address size in 64-bit mode and the memory access wraps a 4-Gbyte boundary and the FP environment is subsequently saved, the value contained in the FP Data Operand Pointer may be incorrect. Implication: Due to this erratum, the FP Data Operand Pointer may be incorrect. Wrapping an 80bit FP load around a 4-Gbyte boundary in this way is not a normal programming practice. Intel has not observed this erratum with any commercially available software. Workaround: If the FP Data Operand Pointer is used in a 64-bit operating system which may run code accessing 32-bit addresses, care must be taken to ensure that no 80-bit FP accesses are wrapped around a 4-Gbyte boundary. Status: For the steppings affected, see the Summary Tables of Changes. AAR40 Writes to Set IA32_MCG_STATUS.MCIP Will Fail Problem: An MSR write that attempts to set the IA32_MCG_STATUS MSR (17AH) MCIP (machine check in progress) bit [2] will fail (e.g. #GP fault on WRMSR) instead of setting the bit. An MSR write that specifies 0 for the MCIP bit will function correctly. Implication: Due to this erratum, software writes to set this bit will not succeed and may cause an unexpected General Protection fault. Workaround: None identified. Status: For the steppings affected, see the Summary Tables of Changes. Specification Update 29 Errata AAR41 Synchronous Reset of IA32_MPERF on IA32_APERF Overflow May Not Work Problem: When either the IA32_MPERF or IA32_APERF MSR (E7H, E8H) increments to its maximum value of 0xFFFF_FFFF_FFFF_FFFF, both MSRs are supposed to synchronously reset to 0x0 on the next clock. Due to this erratum, IA32_MPERF may not be reset when IA32_APERF overflows. Instead, IA32_MPERF may continue to increment without being reset. Implication: Due to this erratum, software cannot rely on synchronous reset of the IA32_MPERF register. The typical usage of IA32_MPERF/IA32_APERF is to initialize them with a value of 0; in this case the overflow of the counter wouldn’t happen for over 10 years. Workaround: None identified. Status: For the steppings affected, see the Summary Tables of Changes. AAV42 During a C-state Exit due to a Pending External Interrupt the System May Hang Problem: Under a precise set of conditions, a processor waking from a C-state due to a pending external interrupt may not complete the exiting process and the system may hang. Implication: Due to this erratum, the system may hang. Workaround: It is possible for the BIOS to contain a workaround for this erratum. Status: For the steppings affected, see the Summary Tables of Changes. AAR43 High Temperature Circuit Marginality Issue May Cause the System to Hang or Auto Reboot Problem: A subset of processors may experience circuit marginality issues when operating at high temperature. Due to this erratum a system hang may occur or the processor may proceed to reboot. Implication: Due to this erratum, the system may hang or auto reboot. Workaround: A BIOS workaround has been identified. Please refer to memory reference code version 1.12 or later. Status: 30 For the steppings affected, see the Summary Tables of Changes. Specification Update Errata AAR44 FP Data Operand Pointer May Be Incorrectly Calculated After an FP Access Which Wraps a 64-Kbyte Boundary in 16-Bit Code Problem: The FP (Floating Point) Data Operand Pointer is the effective address of the operand associated with the last non-control FP instruction executed by the processor. If an 80-bit FP access (load or store) occurs in a 16-bit mode other than protected mode (in which case the access will produce a segment limit violation), the memory access wraps a 64-Kbyte boundary, and the FP environment is subsequently saved, the value contained in the FP Data Operand Pointer may be incorrect. Implication: Due to this erratum, the FP Data Operand Pointer may be incorrect. Wrapping an 80bit FP load around a segment boundary in this way is not a normal programming practice. Intel has not observed this erratum with any commercially available software. Workaround: If the FP Data Operand Pointer is used in an operating system which may run 16-bit FP code, care must be taken to ensure that no 80-bit FP accesses are wrapped around a 64-Kbyte boundary. Status: For the steppings affected, see the Summary Tables of Changes. AAR45 Executing LTR in 64-bit Mode May Access Segment Descriptor Before Checking for Null Selector Problem: When executing the LTR instruction with a null segment selector, #GP(0) should be delivered without accessing the memory in the GDT (Global Descriptor Table). Due to this erratum, such an execution of the LTR instruction in 64-bit mode may access that memory. Side effects of this memory access (e.g. a page fault or EPT violation) that occur may prevent the #GP(0) from being delivered. Implication: Executing the LTR instruction with a null segment selector may incorrectly access the GDT. Intel has not observed this erratum with any commercially available system. Workaround: None identified. Status: For the steppings affected, see the Summary Tables of Changes AAR46 tREFI Exceeds DDR2 / DDR3 Specifications Problem: tREFI (Average DRAM Refresh Interval) is 7.825us which exceeds the 7.8us stated in the DDR2/DDR3 specification. Due to this erratum, the processor will take more time to refresh rows. (example: 64.1ms instead of 64.0ms to issue 8192 refreshes) Implication: tREFI specification is exceeded. Intel has not observed any other issues with DRAM refresh due to this erratum. Workaround: None identified. Status: For the steppings affected, see the Summary Tables of Changes. Specification Update 31 Errata AAR47 Complex Conditions Associated With Instruction Page Remapping or Self/Cross-Modifying Code Execution May Lead to Unpredictable System Behavior Problem: Under a complex set of internal conditions, instruction page remapping, or self/cross modifying code events may lead to unpredictable system behavior. Implication: Due to this Erratum, unpredictable system behavior may be observed. Intel has not observed this erratum with any commercially available software. Workaround: None identified. § 32 Specification Update Specification Changes Specification Changes There are no specification changes in this revision of the specification update. § Specification Update 33 Specification Clarifications Specification Clarifications There are no specification clarifications in this revision of the specification update. § 34 Specification Update Documentation Changes Documentation Changes There are no new Documentation Changes in this Specification Update revision. § Specification Update 35