Intel E5310 Specification Update - Page 38

AJ78. REP Store Instructions in a Specific Situation may cause the Processor to Hang Problem: During a series of REP (repeat) store instructions a store may try to dispatch to memory prior to the actual completion of the instruction. This behavior depends on the execution order of the instructions, the timing of a speculative jump and the timing of an uncacheable memory store. All types of REP store instructions are affected by this erratum. Implication: When this erratum occurs, the processor may live lock and/or result in a system hang. Workaround: It is possible for BIOS to contain a workaround for this erratum. Status: For the steppings affected, see the Summary Tables of Changes. AJ79. A MOV Instruction from CR8 Register with 16 Bit Operand Size Will Leave Bits 63:16 of the Destination Register Unmodified Problem: Moves to/from control registers are supposed to ignore REW.W and the 66H (operand size) prefix. In systems supporting Intel® Virtualization Technology, when the processor is operating in VMX non-root operation and "use TPR shadow" VM-execution control is set to 1, a MOV instruction from CR8 with a 16 bit operand size (REX.W =0 and 66H prefix) will only store 16 bits and leave bits 63:16 at the destination register unmodified, instead of storing zeros in them. Implication: 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. AJ80. Store to WT Memory Data May be Seen in Wrong Order by Two Subsequent Loads Problem: When data of Store to WT memory is used by two subsequent loads of one thread and another thread performs cacheable write to the same address the first load may get the data from external memory or L2 written by another core, while the second load will get the data straight from the WT Store. Implication: Software that uses WB to WT memory aliasing may violate proper store ordering. Workaround: Do not use WB to WT aliasing. Status: For the steppings affected, see the Summary Tables of Changes. AJ81. 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. 38 Intel® Xeon® Processor 5300 Series Specification Update, December 2010