Reissuing graphics cards under the same name but with different specifications is quite common in the graphics market. Thus it is no surprise that NVIDIA chose to attack AMD’s Radeon HD 4870 with a GTX 260 that has a higher number of calculating units.

The GT200 GPU has access to ten Thread Processor Clusters (TPC) – each one with 24 ALUs and eight TMUs respectively TAUs. While the GeForce GTX 280 can access the full number, NVIDIA reduced the number to eight for the GTX 260. In order to close the gap to the Radeon HD 4870, the new GTX 260 will be delivered with nine TPCs. Therefore the overhauled GTX 260 has 216 ALUs and 72 texture units. This equals a theoretical performance benefit of 12.5 percent.

http://www.pcgameshardware.com/aid,660194/Reviews/PCGH_Review_NVIDIA_GeForce_GTX_260_with_216_ALUs/