Acer 5742zg fps drops....

Hey guys, long time no been on this forum. I have a big problem... my acer 5742zg, dual core p6100 2ghz processor, 4gb ram, nvidia geforce 420m experiencing a big fps drops after 10 min of gameplay, sometimes less. I checked temperatures, gpu @ idle 46c, cpu 50c. gaming temp much higher, cpu @ 78~c, gpu @ 75c looks like it allows downclocking to reduce temperature.... when it lags temperature drops to 60c, both cpu and gpu... and then it stop being lagy again...so temperatures rises to 80 and drops down again.... over and over. Allready checked heatsink, there was no dust. what could that be? im on the newer nvidia beta driver, no sign of optimus, atleast i didnt saw it.

Checking with newest hwinfo64. poor acer was ok when i bought it, it happend after a while, maybe half a year....
Power plan is maximum performance, plugged in to a socket.

when idling gpu:
shader clock @ 101
memory clock @ 135

gaming:
shader @ 1000
memory @ 800
gpu fan @ 100%

same shader and memory clocks when temp drops. I am thinking about reapplying thermal paste.

found something interesting.....




..... ACTUALLY it was a dust... damn how did i miss them when looked first time. Now temps stable. Gpu @ 68~. Feels nice to have my lappy back

Lock this thread please.