For quite a while, Intel held the 3D throne because their processors were the most powerful and their FPU performance was adequate for good 3D performance. Both AMD and Cyrix took the role as providers of business processors. For long, AMD was trying to get itself into the high performance ring and to get a reputation as a provider of high performance processors that are good for gaming. They needed a processor that could steal some of the 3D glory from the Pentium II. At the time, AMD’s answer was the K6-2.

It was produced in speeds ranging from 266 to 550 MHz versions and looked just like any Socket 7 processor. But, what makes this processor the K6-2? Why is it any better than the original K6 at higher clock speeds?

Originally named the K6-3D, it makes use of a technology called 3DNow technology. 3DNow is basically an instruction set that contains 21 common instructions used in 3D imagery. Since the most common 3D instructions are contained in the 3DNow instructions, the effect is increased 3D performance with software optimized for 3DNow technology. But, how does this work?

To understand how the 3DNow instruction set accelerates 3D rendering you must first look at the steps necessary in rendering a 3D scene. There is quite a bit to it really. The process is said to be done in four basic steps:

• Physics accuracy – I wasn’t sure what to name this, but basically it means that the FPU of the processor must track the actual physics of the situation being rendered. This means it tracks physical models, their trajectories and locations in space, etc. All of this adds up to make sure that what you see on screen is somewhat accurate to actual physics of the world, at least to how the programmer intended it.
  
• Geometry and lighting – The basic shapes are created from triangles and polygons and lighting source is placed on them. This works the FPU quite intensely.
  
• Triangle transformation – the basic shape created in the last step is divided into many smaller triangles that together make up the shape of the object. This creates the object itself but with no covering.
  
• Pixel rendering – the object created in the last step must now be given a texture, or “skin”. This is called rasterization. In modern systems, this part of the 3D rendering was done by the video accelerator, either on the video card or the dedicated 3D card such as a Voodoo2.

3DNow technology accelerates the first 3 steps. It does this by introducing a few different things. First, the floating point unit is pipelined. In the Intel processors, even though they possess powerful FPUs, they can only make one calculation per clock cycle. With 3DNow, up to 4 FPU calculations can be acted on per clock cycle. This goes right to the hearts of game programmers. Despite what many think, its not the processor speed that limits games so much as the FPU performance. With the increased performance of 3DNow, it leaves a much wider pipeline with which to work. 3DNow goes further to address FPU operands. With MMX technology, only integer calculations were addressed. What’s more, 3DNow provides almost seamless transitions from 3DNow instructions to MMX instructions. This is done with the use of a special instruction which speeds this up.

The catch with 3DNow is that the software must be written to take advantage of it, like MMX. Without 3DNow support, the K6-2 is just a fast K6. So, to experience the gains of 3DNow, the game must either be natively coded for it or make use of 3DNow optimized drivers or API’s. The best method, and that which will get more of a performance hike, is to have the software natively coded for it AND have it use 3DNow supporting drivers. DirectX 6.0 provided support for 3DNow instructions, so games which were only designed to work with the API itself will then automatically took advantage of the 3DNow instructions with DirectX6. Another way to use the new instructions was to get the major video card manufacturers to develop video chipset specific API’s that were optimized for 3DNow. Knowing this ahead of time, AMD worked with the major manufacturers beforehand on this issue, and many developed new drivers that used 3DNow. Obviously, Intel would NOT be creating optimized drivers for their i740 chipset.

So, what about using software not optimized for 3DNow? Well, the K6-2 was still a fast chip. At business software, it was quite fast. When it came down to 3D games not using 3DNow, the Pentium II was still the performance chip. This is because the FPU itself was basically the same as before, and that was weaker than that of the Pentium II. But, when using 3DNow optimized software or drivers, the K6-2 could deliver higher performance than the Pentium II at the same clock speed.

As stated above, the K6-2 was the first AMD processor designed for the 100MHz front side bus(FSB). The 100MHz bus speeds up everything, including the memory accesses, the L2 cache speed, as well as the throughput to the AGP bus. All this came together to provide good performance on business software which makes heavy use of the L2 cache. For this reason, you had to get a Super 7 motherboard in order to use a K6-2 processor. Users had to buy PC100 SDRAM and then push the bus speed up to 100MHz. To really use the chip, you needed a Socket 7 motherboard that supports the 100MHz FSB. It also needed to support the 2.2V setting as well as the necessary multipliers. There were several good boards to choose from at the time, including the FIC VA-503+ and the EPOX EP-58MV/P3C-M.

At the time, there was no doubt that AMD had a winner, and that 3DNow worked. In fact, both Cyrix and IDT would soon be incorporating it into their processors. But, as stated before, the software had to be optimized for it. Without the proper drivers, 3D could range to adequate to just plain crappy. For this reason, some argue that there wasn’t much point in getting such a picky processor when you can just get a Pentium II and get the high FPU performance all the time. This was a valid viewpoint, but AMD knew this and expected it. They planned ahead of time and worked with companies, and they had good 3DNow drivers coming out by the time K6-2 was released. Other software titles came out later with support.

That pretty much sums up this particular chapter in the history of AMD.