Intel E5310 Specification Update - Page 26

AJ30. (E)CX May Get Incorrectly Updated When Performing Fast String REP MOVS or Fast String REP STOS With Large Data Structures Problem: When performing Fast String REP MOVS or REP STOS commands with data structures [(E)CX*Data Size] larger than the supported address size structure (64K for 16-bit address size and 4G for 32-bit address size) some addresses may be processed more than once. After an amount of data greater than or equal to the address size structure has been processed, external events (such as interrupts) will cause the (E)CX registers to be increment by a value that corresponds to 64K bytes for 16 bit address size and 4G bytes for 32 bit address size. Implication: (E)CX may contain an incorrect count which may cause some of the MOVS or STOS operations to re-execute. Intel has not observed this erratum with any commercially available software. Workaround: Do not use values in (E)CX that when multiplied by the data size give values larger than the address space size (64K for 16-bit address size and 4G for 32-bit address size). Status: For the steppings affected, see the Summary Tables of Changes. AJ31. Performance Monitoring Events for Retired Loads (CBH) and Instructions Retired (C0H) May Not Be Accurate Problem: The following events may be counted as instructions that contain a load by the MEM_LOAD_RETIRED performance monitor events and may be counted as loads by the INST_RETIRED (mask 01H) performance monitor event: • Prefetch instructions • x87 exceptions on FST* and FBSTP instructions • Breakpoint matches on loads, stores, and I/O instructions • Stores which update the A and D bits • Stores that split across a cache line • VMX transitions • Any instruction fetch that misses in the ITLB Implication: The MEM_LOAD_RETIRED and INST_RETIRED (mask 01H) performance monitor events may count a value higher than expected. The extent to which the values are higher than expected is determined by the frequency of the above events. Workaround: None identified. Status: For the steppings affected, see the Summary Tables of Changes. AJ32. Upper 32 bits of 'From' Address Reported through BTMs or BTSs May be Incorrect Problem: When a far transfer switches the processor from 32-bit mode to IA-32e mode, the upper 32 bits of the 'From' (source) addresses reported through the BTMs (Branch Trace Messages) or BTSs (Branch Trace Stores) may be incorrect. Implication: The upper 32 bits of the 'From' address debug information reported through BTMs or BTSs may be incorrect during this transition Workaround: None identified. Status: For the steppings affected, see the Summary Tables of Changes. AJ33. Problem: Unsynchronized Cross-Modifying Code Operations Can Cause Unexpected Instruction Execution Results 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 26 Intel® Xeon® Processor 5300 Series Specification Update, December 2010