NVIDIA posted the product page of its GeForce GTX 660 (non-Ti) graphics processor. The chip is currently marked as OEM-only, meaning only NVIDIA's OEM partners have access to it. Its specifications make us believe that the "real thing" (retail version) could be very similar to it.
To begin with, the GTX 660 OEM appears to be based on the same GK104 silicon as the GTX 660 Ti retail. It appears to have been carved out by disabling two SMX units, resulting in a CUDA core count of 1,152. The GPU core is clocked at 823 MHz, with 888 MHz GPU Boost. The memory is clocked at 1450 MHz (5.80 GHz GDDR5-effective), in combination with the 192-bit memory bus width, it churns out 134 GB/s memory bandwidth. Unlike the GTX 660 Ti with its standard memory amounts of 2 GB or 3 GB, the GTX 660 OEM has standard memory options of 1.5 GB and 3 GB. The rest of its feature-set is consistent with that of every other GeForce Kepler family GPU. The GeForce GTX 660 retail could be launched some time in September. It's not necessary that its specifications could match with the OEM version.