Specifications

Product Errata 93
Revision Guide for AMD Athlon™ 64 and AMD Opteron™ Processors
25759 Rev. 3.79 July 2009
166 FXSAVE/FXRSTOR Instructions Use 64-bit Format in
Compatibility Mode
Description
In compatibility mode, FXSAVE/FXRSTOR instructions use the 64-bit memory image format (see
figure 11-8 in the AMD64 Architecture Programmer's Manual Volume 2: System Programming,
order# 24593) as opposed to the non-64-bit format (figure 11-9).
Potential Effect on System
A minor performance loss observed due to saving an additional 16 quadwords to memory.
Suggested Workaround
None required.
Fix Planned
Yes