Problems overclocking GPU mem clock
I'm overclocking my old X1900 AIW card here using ATiTool. It's using a custom Zalman heatsink/fan.
I''m leaving the core clock alone and only tuning the mem clock for now. Stock speed is at 477MHz. I've managed to increase this to 621MHz without any problems.
However, as soon as I set it to 630MHz (it won't do anything if I set it to less than 630), my whole screen just appears as a black and white patterns. The pattern lasts for about 5 seconds and everything goes back to normal, except my clocks have been reset to stock speeds.
My question is, have I hit the limit? Is there anything else I can do to push it past 621MHz?
Thanks for any help. Much appreciated.