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

Author: Anthony Cozzie

Date: 16:29:10 08/26/03

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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



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