VR Zone heard rumors about the specifications about NVIDIA's GeForce GTX 680 (GK104 GPU). The site claims the GK104 die is significantly larger than AMD's Pitcairn but slightly smaller than Tahiti, and that the card itself will be 10 inches long, which is shorter than the Radeon HD 7950 and GeForce GTX 570 cards.
As previous rumours suggested, GTX 680 will feature 1536 SP and 256-bit memory. However, contrary to rumours, NVIDIA has retained the shader hotclock, although the Kepler shaders could be significantly different from its Fermi counterparts which makes it difficult to predict performance. The core will be clocked at 705 MHz and the shaders at 1411 MHz, retaining the 2x shader hotclock from Fermi. GK104 significantly improves upon GF110/GF114's memory controller, setting a new record for reference memory clock at 6 GHz. This equates to a memory bandwidth of 192 GB/s - exactly the same as GTX 580 despite the narrower memory bus.
If VR Zone is right, more details will be revealed by NVIDIA at a launch event on March 12th, with actual product availability slated for March 23rd.