5 ns SDRAM can operate at 200 MHz if all the input signals meet certain timing requirements, which are determined by the SDRAM, graphics chip, and the PCB wire traces connecting the two. Simply put, the signals have to be able to reach the graphics ASIC within 5 nano seconds, or vice versa.

Creative's TNT2 Ultra board (CT6810) uses the exact same SDRAM as that found on the CT6940 board. Yet the the TNT2 SDRAM, which is default clocked at 183 MHz, has proved capable of reaching its rated speed of 200 MHz.

A comparison of the PCB wire traces on the two boards shows that the traces on the CT6940/1 appear to be longer than those on the CT6810 board. With longer trace lengths, the timing of the signals is probably unable to meet the 5 ns requirement in order for the memory to operate at 200 MHz. Given its sheer size and complexity, the GeForce chip may ostensibly impose such a limitation.

PCB Wire Traces
GeForce CT6940/1 (left) TNT2 CT6810 (right)
Note the serpentine nature of some of the traces on CT6940/1.

This issue looks likely to surface with GeForce SDRAM boards from other vendors as well. Creative Labs has ensured a high margin of safety by using 5 ns SDRAMs and the customized clocking utility will only allow a maximum memory clock of 183 MHz.

Transformation is the process of converting 3D coordinates which describe a 3D 'world' into 2D coordinates for viewing on a 2D device, usually a CRT monitor. GeForce is the first consumer level graphics chip to provide transformation calculations to be performed by the graphics chip rather than by the CPU. NVIDIA's press release states that GeForce can transform 15 million polygons per second. Presumably, these figures referred to pre-rasterized triangles and were measured on high-end systems, with the fastest x86 CPU available. After factoring these, the figures should still be taken with a healthy dose of skepticism.

To understand hardware transformation in its present form, it is useful to categorize geometry data into two types, static and dynamic geometry.