Specification Update
37
Errata
BG57.
Performance Monitoring Event FP_MMX_TRANS_TO_MMX May Not Count
Some Transitions
Problem:
Performance Monitor Event FP_MMX_TRANS_TO_MMX (Event CCH, Umask 01H) counts
transitions from x87 Floating Point (FP) to MMX™ instructions. Due to this erratum, if
only a small number of MMX instructions (including EMMS) are executed immediately
after the last FP instruction, a FP to MMX transition may not be counted.
Implication: The count value for Performance Monitoring Event FP_MMX_TRANS_TO_MMX may be
lower than expected. The degree of undercounting is dependent on the occurrences of
the erratum condition while the counter is active. 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.
BG58.
LER MSRs May Be Unreliable
Problem:
Due to certain internal processor events, updates to the LER (Last Exception Record)
MSRs, MSR_LER_FROM_LIP (1DDH) and MSR_LER_TO_LIP (1DEH), may happen when
no update was expected.
Implication: The values of the LER MSRs may be unreliable.
Workaround:None Identified.
Status:
For the steppings affected, see the Summary Tables of Changes.
BG59.
MCi_Status Overflow Bit May Be Incorrectly Set on a Single Instance of a DTLB
Error
Problem:
A single Data Translation Look Aside Buffer (DTLB) error can incorrectly set the
Overflow (bit [62]) in the MCi_Status register. A DTLB error is indicated by MCA error
code (bits [15:0]) appearing as binary value, 000x 0000 0001 0100, in the MCi_Status
register.
Implication: Due to this erratum, the Overflow bit in the MCi_Status register may not be an accurate
indication of multiple occurrences of DTLB errors. There is no other impact to normal
processor functionality.
Workaround:None identified.
Status:
For the steppings affected, see the Summary Tables of Changes.
