Ok, I'm having an odd issue. I'm currently running a Radeon 6950 and using GuiMiner. I'm not the best at OCing, but I copied what someone else did with their card. Using Afterburner, I'm able to get my core clock to 950 without messing with voltages. Odd things is, when I run GuiMiner I get less MHash/s, around 295. When it is not OCed and at the default core clock of 810, I get around 325 MHash/s. After messing around with it some more, I found that setting the core clock at exactly 893 produced the best results at 350 MHash/s. I don't think that this is normal. Would someone please advise. Thank you.

Note: OS is Windows 7 SP1.