Nvidia’s GeForce GTX 280 pictured
The GTX280 will require one 8-pin and one 6-pin connector, while the GTX260 will suffice with two 6-pin connectors. GTX280 sports a 512-bit bus and 1GB GDDR3 memory, while GT260 has to settle for 448-bit and 896MB GDDR3 memory as NVIDIA will disable two memory chips and two clusters of shaders.
GTX280 will have a full setup of shaders, meaning all 240 till be active, while GTX260 has 192 shaders. This may sound like a lot already, but NVIDIA also claims that the shaders themselves are up to 50% faster than the shaders of G80/G92.
Alas, there’s no DirectX 10.1 support, which is kind of poor when you think about it, even if there are extremely few games (any?) out there that actually uses it. Instead NVIDIA has put a lot of work into incorporating the support for its newly acquired PhysX engine, but we still have little to no information about the exact works of that.