NVIDIA GeForce 2 GTS 64MB

Without question, the GeForce 2 GTS GPU contains the most raw power of any video card processor out on the market. With 25 million transistors manufactured on a .18 die process, the GeForce 2 GTS comes clocked at 200 MHz. This power, coupled with the GeForce 2 GTS's quad pipelines, results in an unheard of pixel fill rate of 800 megapixels per second and a textel fill rate of 1.6 gigatexels per second. NVIDIA proclaims that the GeForce 2 GTS will allow the user to play games never imagined before, with fully realistic 3D graphics. The problem is that this fill rate of 800 megapixels per second is only one side of a double edged sword. This edge is known as "theoretical fill rate."

The theoretical fill rate is based off a video card's clock speed and pixel pipeline. From these characteristics of any card, the theoretical fill rate can be calculated. In the case of the GeForce 2 GTS, we have a 200 MHz core clock speed powering 4 pixel pipelines and thus a resulting fill rate of 800 megapixels per second. The theoretical textel fill rate of 1.6 gigatexels per second comes from the fact that the GeForce 2 GTS GPU can process 4 pixels per pipeline, resulting in 800 x 2 textels per second, or 1.6 gigatexels per second. The problem lies in the fact that, while the GPU may be able to push out 800 megapixels per second, the memory bus is almost never fast enough to keep up with the processor.

Herein lies the other edge of our sword. The GeForce 2 GTS GPU is often times able to put out more information than the card's memory can receive at one time. Since all the data sent out from the processor must find its way into and out of the memory at one time or another, the slowness of the memory bus creates a bottleneck in the video card, creating a traffic jam of sorts. As a result of this, the theoretical fill rate of a card is almost never achieved. For this reason it is necessary to introduce a new term into the video card equation: "effective fill rate." Effective fill rate can be defined as the real world speed of a card. Since the video card processor must always make use of the memory bus and the true rendering ability of a card is only as fast as its slowest component, we can conclude that any video card that passes information through the memory bus will almost never achieve its theoretical fill rate, resulting in an effective fill rate. This bottleneck is seen to the greatest extent when in 32-bit color mode, as twice as much data must pass from processor to memory. Unlike theoretical fill rate, which is completely dependent on core speed and pixel pipelines, effective fill rate takes into account that the GPU is not working by itself. Therefore, effective fill rate of a card is dependent on the bandwidth of the memory bus.

Just how dependent are GeForce 2 GTS based cards on their memory bus? Our Overclocking the GeForce 2 GTS guide answers this question by observing the effects of overclocking the memory and core speeds independently. Let's take a look at what the guide found.