Its the same test that ATI's CCC (Catalyst Control Center) uses. You do not need a special tool to do this for you.
With the ATI CCC, you can select your GPU and memory frequecies manually, have it test your card automagically (I like that word!), and if your card screws up upon reboot because you set things too high, it will set it back to the defaults so you can try again.
-S
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