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Technology Stocks : Advanced Micro Devices - Moderated (AMD)
AMD 2.80+1.8%Oct 31 6:40 PM EDTNews

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To: Dan3 who wrote (253382)6/18/2008 8:56:29 PM
From: Ritz of 273491
 
Interesting indeed. From your link:

aceshardware.freeforums.org

Before I saw the AVX documentation, I would have denied that it was possible to add so much new information without making instructions longer. The trick is that it makes one long prefix instead of many short prefixes. One or a few bits in the new VEX prefix contains the same information as a whole 8-bit or even 16-bit prefix or escape code in the current coding scheme. The two VEX prefixes are made out of two obsolete instructions, LDS and LES, which are valid in 16- and 32-bit mode but invalid in 64-bit mode. Certain bits in the VEX prefix that indicate register extensions available only in 64-bit mode are placed in such a way in the VEX prefix that the only values valid in 32-bit mode form an invalid register operand if interpreted as a legacy LDS or LES instruction. This is a solution no less ingenious than the x64 extension invented by AMD.

Looking at the advantages of AVX over SSE5 there can be no doubt that AMD has no choice but to adopt AVX.


The SSE5 instructions will suffer the same fate as AMD's 3DNow instructions. Nobody ever used the 3DNow instructions because they are not supported in Intel processors. They are superseded by the more efficient SSE instructions, but AMD have to keep supporting them in all their future processors for the sake of backwards compatibility. Let's hope that AMD have the guts to drop SSE5 altogether before it's too late. There has been some speculation that they might.


Thanks for posting that Dan.
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