To: Paul Engel who wrote (37220 ) 9/19/1998 7:49:00 PM From: Maverick Read Replies (1) | Respond to of 1571903
3DNoW! outperforms MMX Floating Point SIMD vs. Brute FPU Power AMD saw this development taking place already a year ago, when they decided to improve the K6 CPU by specifically increasing the 3D performance. Whilst Pentium II CPUs are taking their great 3D performance from their brute FPU power, AMD decided to go a more elegant way of approaching 3D performance. The FPU of a CPU can do an amazing amount of complicated floating point calculations, but for 3D games only some of the FPU calculations are needed. Picking these special '3D' calculations and enabling the CPU to do them on several single numbers at the same time was what AMD did. Grabbing and then processing several data packets at the same time is called 'SIMD' or 'single instruction multiple data'. This does not say that only one instruction is needed to work on multiple data, but this means that you do this instruction on multiple data of the same sort at the same time. 3D processing and rendering is using an incredible number of matrix operations. Huge amounts of data has to be processed all the same, usually done one after the other. SIMD can improve this significantly, because grabbing for example, four words and processing them at the same time is obviously faster than grabbing one word four times. The first time SIMD was implemented into a x86 CPU was when the Pentium w/MMX was released. Intel did a lot of work convincing us that MMX would accelerate any kind of multi media, including 3D. Today Intel admits that MMX is mainly good for image processing, MMX2 or 'KNI'='Katmai New Instructions' is supposed to change that significantly though. The difference of the K6-2's new instruction set '3DNow!' and what we know from MMx already is that '3DNow!' as well as KNI are able to do SIMD with floating point numbers (MMX could do this only with integers). Here's where the 3D acceleration takes place. If anyone wants to take advantage of the new K6-2 and 3DNow!, there are three possible options on how that can be done. Either the 3D game is taking advantage of DirectX 6 by using the geometry engine of Direct3D 6, or the game has got its own geometry engine which is using 3DNow! directly. Games that are only written for DirectX 5 or which don't use 3DNow! in their own engine will show only small or no improvements at all with the K6-2. The third option is a 3D chip/card driver that is optimized for 3DNow!. NVIDIA is the first 3D chip manufacturer who supplies a special driver for 3DNow!. It would be sensible to assume that AMD prefers game developers to use 3DNow! directly in their games, but if this should not be an option, it's still of advantage if the game is at least programmed for DirectX 6. It will be up to us consumers to push 3D chip makers into providing drivers that are optimized for 3DNow!. 3Dfx has announced that it supported 3DNow! from www.tomshardware.com