Graphics card underclocks itself?

[turtleduck845]

I have Geforce 8400 GS which is old but playable on old games. On team fortress 2 i started lagging. base clock lowered from 520-407 memory clock from the 700's to 300's and shader clock from 1200's to 800-1000 (sorry forgot)
tempurate were in the 85-92C and when underclocked stayed at constant 77C
any help on what happened

 

[Dunlop0078]

It is likely throttling, temps are too high. The GPU will automatically lower it's clocks to cool down when it gets hot enough. I am not sure the exact temp that will happen with the 8500 GS, 90c if I had to guess.

It is an old card and it is probably due for a thermal paste change if you want to stop the throttling. Or clean it out if the heatsink is caked with dust.

 

[turtleduck845]

i don't think that is the problem the highest i've ever seen it is 90C and it never happened on COD WAW only team fortress 2

 

[Dunlop0078]

i don't think that is the problem the highest i've ever seen it is 90C and it never happened on COD WAW only team fortress 2

Why do you not think that is not the problem? The GPU does not just underclock itself when under full load out of the blue.