You cannot find it because what he says is not true, I've been running with 12.1 eversince it came out, Nothing changed as far as OverClocking is concerned.
Just use MSIa, It has a backwards compatable "bug" in thier "unofficial overclocking" that allows you to Attempt to set Any clock to Anything

win7x64 Cat 12.1 SDK 2.6
crossfire6870 990core 490mem <---Sweet spot for mining
Hell, for awhile i had the cards running at 1020 core and 300mem because i was told 300mem was the best, It's the Most Common best, It's quite specific for the cards.

CGminer also changes clocks Flawlessly
I also hear (NEVER TOUCHED) that Shappire Trix is a good tool.