I have a PNY card with an nVidia Geforce 6200 and 256MB ram, and have nvclock v 0.8 (Beta2) installed. The card has a big vcool fan (pumping air from a duct hogging two expansion slots, right on to the GPU heat sink). I added this to the modprobe.conf.local file:
options nvidia NVreg_EnableAGPFW=1
this is required for the card to have fast writes enabled.
I don't see much hope of overclocking this card very high. I had the memory up to 600MHz from stock 531, and the GPU up to 420 from stock 351, and saw a bit of artifacting using Doom3 to test (the AGP voltage was boosted to 1.8v). The nvclock program claims inability to unlock pixel pipelines on my card.
I could sure use any advice, other than trying to actually volt mod the card hardware, which I don't want to try.