NVIDIA’s GeForce GTX 260 and 280 are based on the GT200 GPU which is made in a 65nm process. Now NVIDIA has performed a die shrink on this design, to 55 nanometers. This results in a lower power consumption allowing new models to be built. The first two cards based on the 55 nm GT200b are the GTX 295 and the GTX 285. While the GTX 295 is a dual GPU design, the GTX 285 follows the traditional single GPU approach. With a marketing name improvement of only 5, the question has to be answered if this card is a worthy upgrade or if you are better off trying to find a great deal on a GTX 280 or GTX 260.
In essence the GeForce GTX 285 is a GTX 280 with about 10% higher clocks and slightly changed PCB and cooler. The cornerstone specs like number of shaders, ROPs, bus width and memory size have remained the same.

The Leadtek GeForce GTX 285 that we have on the testbench today follows the NVIDIA reference design specifications to the letter. I’m certain Leadtek is already working on an overclocked version of the GTX 285.

http://www.techpowerup.com/reviews/Leadtek/GeForce_GTX_285