Sunday, March 21, 2010
What is 3Dnow!
Posted on 7:11 AM by Impress Rabi
In late May, AMD released their new K6-2 processor. One of the main advances that AMD made with the K6-2 was the addition of the 3Dnow! instruction set. Many people have asked, how big a performance difference can an instruction set really have? Well, AMD believes that 3Dnow! is all the K6-2 needs, whereas the K6-2 without 3Dnow! is almost identical in performance to the older K6. But 3Dnow! is very powerful and performance increases have been measured at up to 87% so far. For those wondering exactly what 3Dnow! is, this months column is a basic primer on 3Dnow! and the K6-2.
3Dnow! is a set of extra instructions similar to MMX, but instead of integer acceleration, 3Dnow! is designed to accelerate 3D graphics, through faster FPU performance. However, 3Dnow! is much more beneficial than MMX and it's hardly fair to compare the two. Let's face it, MMX was a joke. It's as if Intel wanted to test their marketing division. When it was released, MMX had almost no support. Only now is it beginning to offer meager performance gains through more widespread support, because of the fact that all new processors include MMX instructions.
3Dnow! gains much of its performance increase due to the use of SIMD (Single Instruction Multiple Data) floating point instructions. Basically the use of SIMD allows multiple operations to be performed at once. Because of this, the K6-2 can perform 4 floating point operations per clock cycle as opposed to 1 per clock cycle with a Pentium-II. Now this doesn't translate directly into games running 4 times faster, as you won't be seeing Quake 2 running at 200fps anytime soon. Just because the K6-2 can perform 4 floating point operations per clock cycle, doesn't mean it always does. Looking at a simple example, any given game sends all its FPU calculations through one data pipe. The K6-2 adds three additional pipes, greatly increasing the bandwidth. But unless the game is programmed to recognize the extra 3 pipes, performance will be the same. However, once the game is optimized to make use of the extra bandwidth of the K6-2, it can use the increased bandwidth for either a performance increase or for creating much more detailed and complex environments, while still running at the same frame rate.
So, unless a game is fully optimized from the start, the full capability of 3Dnow! is not always used. With the requirement of 3Dnow! optimized software to see any real performance gains, are we going to see yet another MMX support fiasco? Not so.
The copyright of the article What is 3Dnow! in Computer Hardware is owned by Michael Christopher Brinton. Permission to republish What is 3Dnow! in print or online must be granted by the author in writing.
3Dnow! is a set of extra instructions similar to MMX, but instead of integer acceleration, 3Dnow! is designed to accelerate 3D graphics, through faster FPU performance. However, 3Dnow! is much more beneficial than MMX and it's hardly fair to compare the two. Let's face it, MMX was a joke. It's as if Intel wanted to test their marketing division. When it was released, MMX had almost no support. Only now is it beginning to offer meager performance gains through more widespread support, because of the fact that all new processors include MMX instructions.
3Dnow! gains much of its performance increase due to the use of SIMD (Single Instruction Multiple Data) floating point instructions. Basically the use of SIMD allows multiple operations to be performed at once. Because of this, the K6-2 can perform 4 floating point operations per clock cycle as opposed to 1 per clock cycle with a Pentium-II. Now this doesn't translate directly into games running 4 times faster, as you won't be seeing Quake 2 running at 200fps anytime soon. Just because the K6-2 can perform 4 floating point operations per clock cycle, doesn't mean it always does. Looking at a simple example, any given game sends all its FPU calculations through one data pipe. The K6-2 adds three additional pipes, greatly increasing the bandwidth. But unless the game is programmed to recognize the extra 3 pipes, performance will be the same. However, once the game is optimized to make use of the extra bandwidth of the K6-2, it can use the increased bandwidth for either a performance increase or for creating much more detailed and complex environments, while still running at the same frame rate.
So, unless a game is fully optimized from the start, the full capability of 3Dnow! is not always used. With the requirement of 3Dnow! optimized software to see any real performance gains, are we going to see yet another MMX support fiasco? Not so.
The copyright of the article What is 3Dnow! in Computer Hardware is owned by Michael Christopher Brinton. Permission to republish What is 3Dnow! in print or online must be granted by the author in writing.
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