The GTX 280 is, on average, the fastest single graphics card you can currently buy but it also comes with a seriously hefty price tag, which most of us would simply never consider stretching to pay. This fact was driven home with all the subtlety of a sledgehammer by ATI, just a week or so later, when it released its own brand new card, in the form of the HD 4870, and proved that great performance didn't have to cost the earth.
Were this the end of it, nVidia might have had a hard time for the next few months as the vast majority of people recognised the limited reason for paying an extra 40 per cent for only (on average) 10 per cent more performance. However, this isn't the end of it because nVidia also just released the GTX 260, which uses the same GT200 chip as GTX 280 but has a few bits of it disabled, so it's slightly slower, but most importantly it costs less. So let's see how it stacks up.
Apart from the slower clock speeds, the GTX 260 is essentially just a GTX 280 with two Texture Processing Units (TPCs) disabled and two ROP blocks also disabled. Because of the way the ROPs are linked to memory this also means the amount of onboard memory has also been reduced to 896MB and overall memory bandwidth has come down to 111.9GB/s.
As the GTX 260 uses the same GT200 chip found in the GTX 280, it's safe to assume that GTX 260s are being made from GT200 cores that have some slight defects. By disabling the defective area, the rest of the chip can still be used without any problems. This rescues revenue for nVidia from otherwise wasted chips and also provides us with cheaper cards that have close to the same performance. This is a theory that is reinforced when you look at the way GT200 is laid out.
The processing units and texture units are separated into distinct sections on the chip with each section working, in a sense, independently. So, if there is a problem in one of the sections of processing cores (the top left one, say), the associated (i.e. neighbouring) texturing units and ROPs can also be disabled without much difficulty.
I won't cover the intricacies of the GT200 architecture in this article, as you can read all about it in my GTX 280 review. Instead I'll move straight to looking at the card itself. And, of course, the performance figures after that.