After my 9800GX2 sort of kicked the bucket I had to switch to my backup 8400GS (free from Black Friday yay). Obviously losing 90% of the performance I used to have is a large jump for me, so I decided to do a pencil mod. I got the resistor down to 535ohms, which is somewhat near the limit at which the card would run (~510ohms). I initially got the card running at 820MHz Core, but after further testing I found it unstable. After a few days later I backed it down to 650MHz (567 is stock)... and it crashed again today. I undid the mod and reset all clocks to stock and the card is still somewhat unstable. It'll get through 3D artifact tests just fine, but it will artifact/crash in 2D games like Osu! after extensive play.

Is it possible to degrade an 8400GS this much? I've only been running it this way for a week or so, and none of the voltage regulators on the card have gotten remotely hot, even during full load.