To give you an indication of the scale of difference across the range, the GeForce 6600 GT has more than three times the fill rate of the 6200 cards, and its vertex processing power is about 40 per cent greater than that of the 6200. A GeForce 6800 Ultra has more than twice the memory bandwidth of a 6600 GT. It has a fill rate of 6.4 gigatexels (compared to 4 for the 6600 GT) and a vertex processing capacity of 600 million per second (the 6600 GT can process 375 million. We'll talk more about texels later.)
Being the most recent series of graphics cards, the chips used in the GeForce 6 series support many of the latest features required by developers to make scenes look good, including support for the most recent DirectX Shader Model (3.0).
The 6 series is available in both AGP and PCIe cards.
Much like the ATI cards, Nvidia has special versions of different chips, clocked at higher speeds or with faster memory. Letters next to the name (such as GeForce 6600 GT) indicate a variation from the standard specifications.
Here's a quick rundown of the variations:
Turbocache - a variation of the GeForce 6200, the Turbocache is available in only the PCIe version of the card, and is designed as a low cost solution that partially uses main memory for graphics operations.
TD and TDH - The T indicates the card has TV-out, the D indicates it has DVI out and the H indicates it has Hardware Monitor Function.
LE - a trimmed down version of the basic card, using a chip running at a slower clock speed with possibly fewer pixel pipelines.
XT - the chip and memory run at slightly slower clock speeds than the "basic" card. XT cards are thus a little slower and a little cheaper than the basic card . This can be confusing, since ATI uses "XT" to indicate a high-end card.
GT - in the 6600 and 6800 cards, a "GT" designation means that the card uses GDDR3 memory instead of DDR memory. GDDR3 memory is a much faster type of memory than DDR, running at up to 1050MHz. A GT card will be somewhat faster than a "vanilla" version of a card.
Ultra - a considerably faster version of the chip than the vanilla version. The chip and memory run at higher clock speeds than the normal version.
Ultra Extreme - faster again than the Ultra.
SLI - the card is capable of working with an identical card in an SLI configuration (see below). SLI cards are all PCIe.