Originally Posted by CryptiK
The 600 series cards do not downlock they run at different speeds. Some have reported GPU utilization is lower on the faster card, as if it's pausing to wait for the slower card to finish the work and move on. Not sure about the 500 series but I think that clock matching business from years ago certainly does not occur anymore.
It's actually never occurred.
It may be that the higher clocked card gets lower utilization, such that the actual performance is LIKE what it would be at the slower of the two clocks ... but there has never been a time/card where running SLi with cards with mismatched clock speeds actually saw the higher clocked card being 'downclocked' to match the lower of the two clocks.
It's what I would call an 'urban myth' ... although like I say, the actual end-result in terms of performance is similar, that particular description of what went on was never accurate in the literal sense