Radeon HD 4890 rival Geforce GTX 275: Specifications sighted
AMD's Radeon HD 4890 is in the starting blocks but Nvidia wants to counter with the Geforce GTX 275.
The clock speeds of the Geforce GTX 275 have apparently been fixed and shall be 633/1,404/1,161 MHz (GPU/Shader ALUs/VRAM). The memory interface of the graphics card is supposed to have a width of 448 Bit. Thus the memory space is fixed, too - 896 MiByte are probable according to Expreview. So it seems to be true that the Geforce GTX 275 matches with the Single GPU version of the GTX 295.
For comparison: The clock rates of a Geforce GTX 285 are 648/1,476/1,242 MHz and therefore only slightly higher. Though it offers a 512 Bit memory interface and 1,024 MiByte in the default specification. Fudzilla reports that the GTX 275 will have 240 shader processors and is supposed to cost about 250 Euro in Europe including a dual slot cooler. The price level corresponds to the already listed Radeon HD 4890 graphics cards. There already are benchmarks available, too.
Grafikkarten-Rangliste 2016: 32 Radeon- und Geforce-GPUs im Benchmarkvergleich [Oktober]