Possible details of NVIDIA's upcoming mid-range GTX 660 and GTX 650 graphic cards along with performance numbers have been revealed through various Chinese forums.
Even though NVIDIA did launch the GTX 660 Ti version last month, A Non-Ti variant was also confirmed for launch later. The Non-Ti version does exist though in the form as an OEM only part based on the GK104 core, The consumer version is supposed to feature the GK106 core which would allegedly feature 960 Cores, 980MHz/1033MHz Core/Boost clock and a 2GB GDDR5 memory running at 6GHz effective speed along a 192-bit interface.
Middle Eastern hardware portal arabpcworld managed to get a die shot of this GK106 core codenamed GK106-400-A1 which measures around 240mm2 and a better comparison of the die with GK104 core was given by videocardz which you can see below:
It is said that this GK106 based GTX 660 launches in early along with the GTX 650 which is based off the GK107 core. Exact dates are said to be in-between 6th-12th September. Specifications of the GTX 650 are said to be the same as GT 640 though higher frequencies of 1058MHz and a 6-Pin connector amount for additional performance.
Finally, we have the first performance numbers of these new mid-range GPUs which are also compared to the GTX 660Ti. They have been tested in Heaven 3.0, Dirt 3 and an Unknown title at 1080P resolution with max settings:
As far as pricing is concerned, The GTX 660 would fall for $229-$249 while the GTX 650 would go for around $149 US.