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Subject: Re: windows for AMD64 - MMX not 64-bit threadsafe

Author: Eugene Nalimov

Date: 17:03:16 08/26/03

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On August 26, 2003 at 19:29:10, Anthony Cozzie wrote:

>On August 26, 2003 at 18:58:20, Eugene Nalimov wrote:
>
>>On August 26, 2003 at 18:32:49, Jeremiah Penery wrote:
>>
>>>On August 26, 2003 at 17:42:42, Gerd Isenberg wrote:
>>>
>>>>Hmm... that makes using these register impossible - at least with a
>>>>multithreading approach. Eight bitboard (or float) register for nothing, or only
>>>>a few percent faster context switch. Ok, there are still the 16 (14) general
>>>>purpose bitboards and 32 XMM bitboards, nevertheless...
>>>>
>>>>Gerd
>>>>
>>>>
>>>>Porting Windows® Device
>>>>Drivers to AMD64 Platforms
>>>>
>>>>Page 7
>>>>
>>>>• Convert media instruction to SSE/SSE2 Instructions
>>>>
>>>>Microsoft Windows for AMD64 will not context switch x87, 3Dnow!, MMX for 64-bit
>>>>native threads. This code may be converted to SSE/SSE2 through the use of
>>>>intrinsic functions.
>>>
>>>What exactly does this paragraph mean?  If it means what it seems to mean, I
>>>don't see how it could get away with that for regular x87 code.  I also don't
>>>see why that means that the MMX registers are not thread-safe.  If it means
>>>something else, it's certainly not very clearly stated.
>>
>>That paragraph means that 64-bit code on AMD64 Windows cannot use MMX or x87
>>instructions.
>>
>>Thanks,
>>Eugene
>
>isn't x87 the floading point unit?  So you are saying Windows for Opteron won't
>be able to do any floating point math at all?
>
>anthony

No, I am saying that you have to use non-x87 to do FP on Windows for AMD64 --
e.g. SSE2.

Thanks,
Eugene



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