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Advanced Micro Devices introduced the 3DNow!  instruction set back in the K6-2 days to perform single instruction multiple data (SIMD) instructions, otherwise known as vectorized instructions. The 3DNow! was meant to greatly improve performance of floating point operations, but not a lot of programs actually took advantage of the instruction sets. As a result, over a decade later AMD decided to pull the plug and its future chips will not support 3DNow!

"[Since the introduction of 3DNow!], we have added many SIMD instruction sets to our processors, such as the widely used Streaming SIMD Extensions (SSE) instruction set and its successive versions. 3DNow! instructions are being deprecated and will not be supported in certain upcoming AMD processors. In those processors, the 3DNow! Instructions feature flag bit will not be set," wrote Sharon Troia, senior developer relations engineer.

Around the same time as 3DNow! instructions were developed, programmers were accustomed to using a model of ‘try and catch’ to check if a processor supported an instruction or instruction set.  This is when the application ‘tries’ to execute an instruction to see if it’s available. If the application receives an Undefined Exception (#UD) from the processor, it believes the instruction set isn’t available. These types of applications may not do well under newer virtual machines.  That’s subject for another blog though.

The 3DNow! versions of the PREFETCH and PREFETCHW instructions are now in a class of their own and AMD plans to continue to support them.

It is most likely that mainstream applications have non-3DNow! code path to take, such as an SSE path. 

Tags: AMD, 3DNow!, Athlon, Phenom, Bulldozer,


Comments currently: 3
Discussion started: 08/21/10 02:05:49 AM
Latest comment: 08/22/10 10:32:32 AM


Why programmers were accustomed to using a model of ‘try and catch’ if instructions feature flag bits exists?
What are benefits of not having the certain instruction sets in CPU?
If some programs were using the ‘try and catch’ model, that is problematic under newer virtual machines, they will not change its behaviour automagically only because new CPU does not support the certain instruction set.
0 0 [Posted by: KonradK  | Date: 08/21/10 02:05:49 AM]

What are benefits of not having the certain instruction sets in CPU?

Smaller and less complex cpu.

Its a pity 3Dnow never got popular as it seems to have been better than the almost clone that became SSE, but considering how few apps support it, i can certainly understand the decision.
0 0 [Posted by: DIREWOLF75  | Date: 08/21/10 04:59:33 AM]

Yep .. too bad 90% of programmers are generally living half a century ago in the x86 / binary world. Actually every special instruction set such as MMX and 3DNow! and SSE was a desperate call from the hardware makers telling the programmers how to optimize for their architecture. Look at PS2! Look what a tight optimizing scheme can get out of an older architecture. But do today's programmers know how to optimize? Nope! It's a wonder if they manage to use some SIMD instruction from SSE2 or 3 ... but not more.3D Now! never got used because most of programmers are .. let's say "limited and far behind".Belive me , I know this for a fact and I was amazed to see that none of my colleagues in the university knew what a x86 translate unit was.
0 0 [Posted by: East17  | Date: 08/22/10 10:32:32 AM]


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