I've had a similar problem with my card, a Sapphire X800GTO 256 AGP, although it's unlocked and overclocked. Usually it runs fine at 540 core and 590 mem (it's R480 core and 1.6ns ram). The core goes higher, but the ram doesn't. It refuses to do 600, and will crash within 30 seconds. Thing is, I've been running it this way for a while, upgraded to the 6.11 Catalyst drivers, and all was well. A few minutes ago, while playing lost cost, I got a nice plaid of green, pink, and white all over my screen. I know my card isn't overheating. I have a Zalman VF900 on the core and it routinely registers no higher than 32c at idle and 45c in game. The ram isn't too warm either since I put the tiny zalman heatsinks on it. I even put a heatsink on the rialto bridge, to cool it down, used alumina epoxy since it's non-conductive/capacitive, and ceramique on core for the same reason. I've run it like this for a month, and it won't crash, unless it's Jedi Academy, and then it just goes out in a few minutes. But it crashed in HL2...after a half hour in the game. It runs fine at stock speeds and unlocked. Is the card bad? Should I be sending it back, or should I just lower the clock and live with it? Granted, system specs are Athlon XP 3000+ (Locked) @ 2.25 Ghz on 1.65 volts. Abit NF7S-2.0 board. 1GB of Samsung 333 RAM in dual channel mode OC'd slightly to 174 Mhz, 2-3-3-7-2T timings on 2.7 volts. 120G Hitachi 180GXP HDD, 1 Lite-on 52 CD drive, 1 Lite-On DVD Burner, and 7 fans, all powered by a PC Power & Cooling Silencer 470. All voltages off the power supply are within 1% (really .5%) of their rating. Mobo northbridge voltage is 1.5 volts, AGP is 1.5.
I'd really like some help too, guys, this is driving me nuts. Only thing I haven't tried yet is upping voltage to the vid card slightly (never liked the idea) to 1.6V. Would that really help? Thanks much for any help.
~Cow