Well, I've made an interesting discovery today while testing and refurbing an old Radeon 9700 Pro that I picked up in excellent condition.
I gave it a quick test in my Abit NF7-S 2.0 (Nforce 2 Ultra + Athlon XP) system. After a minute or so the PCB behind the GPU die was definitely hotter than the heatsink, so I knew the contact was pretty poor. I shut it down, but there weren't any artifacts up to that point (in Windows XP, but without drivers installed yet), so I knew it was at least worth improving the cooling. When I took the cooler offer, I saw that someone had already been in here, and that the stock thermal putty\crust (whetever it was...) on the heatsink had already been carved away in a square around the die and there was a tiny dot of what looked like Arctic Silver in the center... obviously making terrible contact with the cooler. There also still seemed to be a bit of a "rim" of old thermal crud around the die, so I carefully scraped that down to level it out.
To avoid having to remove the notorious big shim around the die (sounds like a nightmare), I sandwiched a thin 0.3mm copper shim between the die and the heatsink with thermal paste. I also installed some new clips since they were a bit less fiddly than the originals. During testing the heatsink was basically the same temp as the back of the PCB so the copper shim definitely did the job.
However, after I installed drivers the system would just lose display signal when loading Windows. BUMMER. I tried a few things and basically was ready to call it dead. Then, I read some posts online about this happening all the time back in the day... especially on higher-end Athlon XP systems, even some speficially mentioning the NF7-S 2.0! In some cases a different power supply fixed it. Rather than mess with all that, I just dropped it into another system I have, running an EpoX 9NDA3J (Nforce 3 Ultra) and an Athlon 64 X2 4200+. The card seems to be working perfectly fine on the second system! I haven't tested and heavy 3D applications yet, but it is working with whatever drivers the system found to install by default, and I ran the brief Directx 9.0C dxdiag 3D acceleration tests with no issues at all.
So, if you've got a 9700 Pro that seems dead, definitely try it in another system. I guess these things were quite finicky back in the day. It is either due to a high demand on the voltage rails, chipset\BIOS quirks or possibly even drivers. If I am able to narrow it down any further, I will post back here again. I will say, both systems are running the same Seasonic 550HT 550W 80Plus White with 30A on the +5v rail and multiple 12v rails, so I'm not sure if the power supply would be to blame. If it is, then maybe +5v rail is the culprit. The board is running a 1700+ Thoroughbred B core at 2Ghz, so it shouldn't be too power hungry, but the A64 is probably more balanced toward 12v.
I thought for sure the thing was dead, so I am quite pleased. 😀