1950 Pro Overclock question

I have an Sapphire 1950 Pro 512MB AGP card w/Accelero X2 cooler on it in my system. I had it overclocked to
610/1440 for a long time, which is ok for the gpu and pretty good for the memory from what I understand of these cards (stock is 580/1400).
Anyway, I couldn't leave well enough alone, I wanted to try to up the core clock more, so I brought both back to stock and started using ATI tray tools to up the clock and test for artifacts. For the core, I got up as high as 640 before I'd lock up, so I figure if run at 620 I should be ok (have to test that more though).
But the real problem - now, no matter what I do, I can't get the memory to go over 1404 (yes, thats a -four-, I didn't have a fit of dyslexia). I tried keeping the core at stock and just tweaking the memory but as soon as I go just slightly over stock speeds on it, it now locks up the system.
I'm perplexed - I used to have it at 1440 and now just a hair over stock and it locks up system. Anybody have any thoughts on what the issue could be? Its not a heat issue as I've looked at gpu and vrm temps and they're fine. I was going to try to up the voltage on the agp port, but I wasn't sure if that would make any diff for the memory or not. Any thoughts?

Thx,
Sdrac

Have you tried adjusting voltages for the memory and core?
It can be done from ATItool's settings.

Anyway, give Rivatuner a try as the above poster suggested. Might give you better results

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