G x 2 = Yow!
To give you a better sense of the kind of wallop this one graphics card packs, have a look at the theoretical numbers before. On paper, at least, the GX2 is staggering.

The GX2 outclasses Nvidia's previous top card, the GeForce 8800 Ultra, in every category. More importantly, perhaps, it matches up well against the Radeon HD 3870 X2—ostensibly its closest competitor, although the 3870 X2 is now selling for as low as $419. The two cards are fairly evenly matched in terms of pixel fill rate, memory bandwidth, and peak shader power, but look closely at the 9800 GX2's advantage over the 3780 X2 in terms of texture filtering capacity—it leads 76.8 to 26.4 Gtexels/s. The gap closes with FP16 texture formats, where the GX2's filtering capacity is chopped in half, but it's still considerable.

We can, of course, measure some of these things with some simple synthetic benchmarks. Here's how the cards compare.

The 9800 GX2 trails the 3870 X2 in terms of pixel fill rate, but it makes up for it with a vengance by more than doubling the X2's multitextured fill rate, more or less as expected. In fact, in this test, the GX2 shows more texture filtering capacity than three GeForce 8800 Ultras or four Radeon HD 3870s.

Somewhat surprisingly, the Radeon HD 3870 X2 takes three of the four 3DMark shader tests from the GX2. But will that matter in real games?