I've had one major problem with my Pentium III since I put a Matrox Parhelia graphics card in it: Noise.
The cooler on the Parhelia either had a busted bearing, or it was just poorly designed, cause it had a loud, very high pitched whine that totally got on my nerves.
After a recommendation from somebody on this very forum, I ordered a cheap hsf from Hong Kong, which was supposed to be really good. After over a month of waiting, I concluded that it never would arrive.
Instead I went all out and bought a Zalman ZM80D-HP passive heatpipe cooler.
After installing it, the card is now (obviously) completely silent, but it does seem the Parhelia, especially the memory, runs quite hot. I've temporarily installed an old 80mm case fan in the PCI slot next to the Parhelia,
to add some extra cooling, and this does seem to work well, but when I get a new case for this system, I'm going to give it some better airflow.
The Zalman cooler really has done the job though, as the system is now much more quiet, and it also gave the card a really badass look.
I can totally recommend this cooler 😀