CPUID with AMD support test piece.

[Rockoon]

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AuthenticAMD
Cannot Identify x86 Processor
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n/a - INTEL Only
n/a - INTEL Only
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This is an AMD Phenom II x6 1055T  "Thuban"

The specs taken from the Phenom II tech sheet:

Including support for SSE, SSE2, SSE3, SSE4a, ABM, MMX, 3DNow! technology and legacy x86

The Advanced Bit Manipulation (ABM) was introduced with K10 and consists of 2 instructions:

POPCNT - counts the number of bits set in a word.
LZCNT - counts the number of leading zero bits in a word.

Your program says SSE4a is not available, and maybe it isn't.. but the technical specs say that it is. Havent tried them.

[Rockoon]

but running 32 bit mode (XP) so the 3DNow instructions are not available

??? 3DNow should work fine in 32-bit mode. It came out at a time when Intel was still dreaming of SSE.

[jj2007]

The Advanced Bit Manipulation (ABM) was introduced with K10 and consists of 2 instructions:

POPCNT - counts the number of bits set in a word.
LZCNT - counts the number of leading zero bits in a word.

In case somebody is confused about the "word": popcnt is also available on Intel, and not limited to a word:

POPCNT r16, r/m16
POPCNT r32, r/m32
POPCNT r64, r/m64 (64-bit mode)

http://software.intel.com/file/17971/

Re LZCNT, does that anything different than bsf?

[Rockoon]

Re LZCNT, does that anything different than bsf?

I'm pretty sure that they are functionally different in the degenerate case, where the operand is 0.

Oh, and I think you mean BSR, not BSF.


The latencies are quite different as well. On AMD the LZCNT is supposedly 2 cycles, whereas BSR is still a vector path with 6 cycles of latency.

edit: woops, it doesnt work on xmm regs

[jj2007]

Re LZCNT, does that anything different than bsf?

I'm pretty sure that they are functionally different in the degenerate case, where the operand is 0.

Most probably yes (I can't test it). BSF/BSR set the zero flag for the null operand, which is certainly not the best solution.

Oh, and I think you mean BSR, not BSF.

:U

[KeepingRealBusy]

but running 32 bit mode (XP) so the 3DNow instructions are not available

??? 3DNow should work fine in 32-bit mode. It came out at a time when Intel was still dreaming of SSE.

You are absolutely correct, I misread the PDF.

Dave.