Nvidia released the GeForce GTX 660 Ti less than one week ago. Now, the company's website has added specifications for an "OEM" derivative of the card. Meant for system builders, the GeForce GTX 660 (OEM) appears to be based on the same GK104 GPU as its Ti sibling. While the Ti disables one of that chip's eight SMX units, the GTX 660's 1152 shader ALUs suggest the lights have been turned off on two SMX engines. Nvidia's product page makes no mention of whether the number of ROP partitions has changed, though. The GeForce GTX 660 Ti uses three of the four ROP partitions on the GK104, and I'd expect the same number to be active in the OEM card.
In addition to fewer ALUs, the GeForce GTX 660 sports lower clock speeds. The card has an 823MHz base clock and an 888MHz boost rate, both down about 100MHz from the Ti. The memory clock is slower, as well. Nvidia quotes a 5.8 GT/s memory transfer rate, which is admittedly a drop of only 200 MT/s. Although the OEM variant's memory interface width remains 192 bits wide, cards will be available with 1.5 or 3GB of onboard memory rather than the 2GB found on the Ti.
Trimming units and lowering clock speeds allow Nvidia to squeeze the OEM model into a smaller power envelope than its big brother. The GTX 660 Ti has a maximum power rating of 150W and requires dual 6-pin PCIe power connectors, but the OEM flavor is rated for 130W and demands just one PCIe power lead.
This OEM offering could hint at what to expect from an eventual GeForce GTX 660 destined for store shelves. Nvidia released the GeForce GTX 560 just a few months after the Ti version of that card, and it doesn't have any Kepler-based products selling for less than $300. A hypothetical GeForce GTX 660 might make a good foil for the recently discounted Radeon HD 7870 GHz Edition at $249. Thanks to Fudzilla for the tip.