I've had an XFX Radoen 7750 2GB Core Edition for a while now, and ever since the first day that I got it, I haven't been able to overclock the DDR3 Memory on it through Catalyst control center. I overclocked the core with no problem, from 800 to 900 MHZ. But the RAM just stays at 667 MHZ, and if I try to overclock it, horizontal tearing and color glitches start appearing randomly, about 1 or two glitches per second. It works perfectly fine and normally when the RAM is not overclocked. I have the power consumption turned up to 15 % (That's 63 watts), and the max I can go is 20% (66 watts). Manual fan control is off.
What could be causing the GPU to glitch when I overclock the RAM? I know that DDR3 RAM goes a lot faster than 667 MHZ, so what gives?
Thanks to anybody who can help.