Thanks for the ideas. I must have turned my brain turned off earlier in the week.
I've tested the 5800 further using your suggestions:
- Running 3DMark03 with AA and AF does not activate the fan. It does halve the final score: ~5200 to ~2800.
- Running 3DMark03 with 2D clocks at 75/175 did not change the results significantly.
- Booting with 2D Clocks set at 75/175 caused screen corruption when the WinXP Pro desktop loads. This bears further investigation.
- GPU temperature never exceeds 60°C for the non-ultra card, even when running for a while overclocked to 500/1000, which is more than I can say for my Ultra, which reaches 72°C at the same clocks under UT2003 and 3DMark.
- FWIW this 5800 is an ASUS V9900TD with the reference fan, not the Abit OTES fan.
- Don't have Neverwinter Nights, but I might have to get it soon.
My guess is that I was simply paranoid about this card's performance after a RAM failure on another graphics card last month. Overall I'm not disappointed at the 5800 non-Ultra, it's just that I didn't expect NV30 non-Ultra benchmarks to diverge so much from NV30 Ultra.
I used to drive a Heisenberg, but whenever I'd glance at the speedometer, I'd get lost.