Just wondering if AMD/Nvidia or their partners bin their GPUs. And how exactly does the process work? I know that CPU manufacturers bin their processors with tester machines (ex. http://www.teradyne.com/std/ ). Do they do the same with GPUs?
The obvious answer would be yes, they do bin gpu's. That's why the same chip can end up with 3 different SKU's (stock keeping units).
A 5870 and 5850 are both of the same chip (Cypress), and The gtx 480 and 470 are also the same (Fermi).
Sometimes chips are bad but can be salvaged through using higher voltages and cutting off bad silicon. Higher volts = more stable performance when the silicon isn't good. These are chips like the 5830 (Cypress) and gtx 465 (Fermi) - physically identical to their more illustrious parents except cut down into slower working parts.
As a physical test, I believe they use certain kinds of dye which shows how good or bad chips are. That is probably what the "binning" name came from. A chip gets "binned" into a certain bucket depending on how it performs on the dye (voltage) test.
Chip binning will be done at AMD/nVidia I think (splitting a cypress into a 5850 or 5870), although further binning can then be done at their partners, eg Sapphire or EVGA, and that will theoretically allow them to keep better parts for more expensive cards.
The 460 is particularly well suited to that. NVidia clocked it absurdly low to not eat into their 465/470 sales, so some of those GPUs can clock very high without effort. It's equivalent to what would happen if AMD decided to make all Barts GPUs into 6850s and didn't make a 6870. You would see OC 6850s clocked to the sky since all the chips that would be 6870 would be in the pile. You're already going to see people OC 6850s close to 6870 speeds because the 'almost 6870' chips are all 6850s.