Not long after the rumour mill at 3DCenter came up with specifications and details forAMDs Tahiti, they have now moved onto NVIDIAs first next-gen 28nm chip - rumoured to be GK104. Succeeding GF114 and the GeForce GTX 560 cards (except the 448 Core version), GK104 is rumoured to release in Q1 2012 with a smaller die than GF114.
GK104 is reported features between 640 and 768 SP, 80-96 TMU and either 256-bit or 384-bit memory interface. The performance is likely to be a bit faster than GeForce GTX 580. To make an early launch possible, the speculation mentions GK104 could be a hybrid between Fermi and Kepler, with the first true Kepler part coming with GK100. GK104 also aims at a die size smaller than GF114, presumably to undercut AMDs Tahiti and increase yields for an early release. If GK104 does release in early-mid Q1 2012, as rumoured, it will go up directly against Radeon HD 7800 series / Pitcairn, also releasing around the same time.
Meanwhile, the flagship GK100 chip could release in Q2 2012, with early speculation pointing towards estimated specifcations of 1024 SP, 128 TMU, 64 ROP and a 512-bit memory interface, and performance closing in on GTX 590.
Much of the information coming from 3DCenter is contrary to the previously leaked roadmap by 4Gamers. At this early stage such contradictory speculation is the norm, and all such rumours must be taken with a grain of salt.