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

Author: Eugene Nalimov

Date: 15:58:20 08/26/03

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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



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