It is a heat issue. After checking on the web I figured out how to easily pull the retaining pins off the stock ATI HSF and remove it. It's really easy.
(If you're interested, the ATI push pins are two piece, you use needle nose pliers to pull straight up on the pin head, it easily comes out, then the second part of the push pin can be pushed back throught the video card from the backside.)
So I got a Vantec CPU cooler, the ICEBERQ 4. However what Vantec does not mention in their instructions (even though it's supposed to fit the ATI Radeon 9800 Pro) is that the Radeon 9800 uses a metal shim around the outside of the GPU which keeps the cooler base from full contact with the chip. The Stock ATI cooler has a slight raise on the cooler base that fits over the chip, the Vantec does not, it's perfectly flat. You can remove the shim from the card with an exacto knife so the vantec has full contact, but that will surely void the warranty.
I tried using a little extra Arctic Silver 5, but the artifacts were far worse. Clearly the Vantec was not in full contact and not cooling properly. So I reinstalled the stock ATI HSF and am RMAing it now.
Here's something interetsing. I installed an Nvidia FX-5200 Ultra from my old system in my new Athlon 64 system to hold me over till the Radeon is returned. I ran FutureMark 03 and got 1/2 of the score as my ATI Radeon did. In fact Battle of Proxycon was so choppy as to be hard to watch. This was to be expected given the vast difference in these cards.
But in AHII, there was almost no discernable difference! The 5200 Ultra has great frame rate. The game plays 99% as well with the 5200 Ultra as with the 9800 Pro.
It just shows how CPU intensive AH is compared to other games that are GPU intensive. I would tell folks today when budgeting for a new system that primarily plays AH, to put more $ in the CPU and less in the graphics card.
