Specifications

Product Errata 79
Revision Guide for AMD Family 10h Processors
41322 Rev. 3.84 August 2011
337 CPU Instruction-Based Sampling Fields May Be Inaccurate
Description
The processor may experience sampling inaccuracies when Instruction-Based Sampling (IBS) is
enabled in the following fields:
• IBS Op Data Register[IbsCompToRetCtr] (MSRC001_1035[15:0]) may be incorrect for
floating-point instructions, when IBS Op Data 3 Register[IbsStOp] (MSRC001_1037[1]) is
set, or when IBS Op Data 3 Register[IbsLdOp] (MSRC001_1037[0]) is set.
• IBS Op Data 3 Register[IbsDcMissLat] (MSRC001_1037[47:32]) may be incorrect if the
processor tags a load instruction for IBS and the data for a retired store operation is in the
process of being written to the data cache. As a result, IbsDcMissLat may start counting early
when the load instruction is tagged and may be non-zero on a data cache hit.
• IBS Op Data 3 Register[IbsDcStToLdFwd, IbsDcL2TlbHit2M, IbsDcL2TlbMiss]
(MSRC001_1037[11, 6, 3]) may be incorrect when IBS Op Data 3 Register[IbsDcStBnkCon]
(bit 10) or IBS Op Data 3 Register[IbsDcLdBnkCon] (bit 9) are set.
• IBS Op Data 3 Register[IbsLdOp, IbsStOp] (MSRC001_1037[1:0]) may be set incorrectly for
non load/store instructions that are tagged for IBS. Other fields in MSRC001_1037 may also
be set based on an unrelated instruction. This occurs when a load/store instruction is tagged
and then a branch misprediction causes it to be canceled. When a new instruction is tagged for
IBS, it may trigger incorrect information if the same buffers are used for both instructions.
This typically would not result in a statistically significant number of incorrect samples.
• IBS Op Logical Address Register (MSRC001_1034) may not point to the sampled instruction
when highly specific conditions are met for the sampled and surrounding instructions. In these
cases, the address reported may be 16 bytes past the sampled instruction and may not point to
the beginning of an actual instruction.
Potential Effect on System
Inaccuracies in performance monitoring software may be experienced.
Suggested Workaround
None.
Fix Planned
Yes