Update

30 Intel
®
Xeon
®
Processor E7-8800/4800/2800 Product Families
November 2014 Specification Update
BP51. CR0.CD Is Ignored in VMX Operation
Problem: If CR0.CD=1, the MTRRs and PAT should be ignored and the UC memory type should be
used for all memory accesses. Due to this erratum, a logical processor in VMX
operation will operate as if CR0.CD=0 even if that bit is set to 1.
Implication: Algorithms that rely on cache disabling may not function properly in VMX operation.
Workaround: Algorithms that rely on cache disabling should not be executed in VMX root operation.
Status: For the steppings affected, see the Summary Tables of Changes.
BP52. REP MOVS/STOS Executing with Fast Strings Enabled and Crossing
Page Boundaries with Inconsistent Memory Types may use an
Incorrect Data Size or Lead to Memory-Ordering Violations
Problem: Under certain conditions as described in the Software Developers Manual section “Out-
of-Order Stores For String Operations in Pentium 4, Intel Xeon, and P6 Family
Processors” the processor performs REP MOVS or REP STOS as fast strings. Due to this
erratum fast string REP MOVS/REP STOS instructions that cross page boundaries from
WB/WC memory types to UC/WP/WT memory types, may start using an incorrect data
size or may observe memory ordering violations.
Implication: Upon crossing the page boundary the following may occur, dependent on the new page
memory type:
• UC the data size of each write will now always be 8 bytes, as opposed to the
original data size.
• WP the data size of each write will now always be 8 bytes, as opposed to the
original data size and there may be a memory ordering violation.
• WT there may be a memory ordering violation.
Workaround: Software should avoid crossing page boundaries from WB or WC memory type to UC,
WP or WT memory type within a single REP MOVS or REP STOS instruction that will
execute with fast strings enabled.
Status: For the steppings affected, see the Summary Tables of Changes.
BP53. The Corrected Error Count Overflow Bit in IA32_ MC0_STATUS is Not
Updated After a UC Error is Logged
Problem: When an uncorrected error is logged in IA32_MC0_STATUS (MSR 0x401, corrected
errors will continue to update the lower 14 bits (bits 51:38) of the Corrected Error
Count to overflow. However, the sticky count overflow bit (bit 52) of the Corrected Error
Count will not get updated.
Implication: The Corrected Error Count Overflow indication will be lost if it occurs after an
uncorrectable error has been logged.
Workaround: None identified.
Status: For the steppings affected, see the Summary Tables of Changes.
BP54. The Upper 32 Bits of CR3 May be Incorrectly Used With 32-Bit Paging
Problem: When 32-bit paging is in use, the processor should use a page directory located at the
32-bit physical address specified in bits 31:12 of CR3; the upper 32 bits of CR3 should
be ignored. Due to this erratum, the processor will use a page directory located at the
64-bit physical address specified in bits 63:12 of CR3.
Implication: The processor may use an unexpected page directory or, if EPT (Extended Page Tables)
is in use, cause an unexpected EPT violation. This erratum applies only if software
enters 64-bit mode, loads CR3 with a 64-bit value, and then returns to 32-bit paging
without changing CR3. Intel has not observed this erratum with any commercially
available software.