Performance drops when OC'ing

Asus X79, 4930k, EVGA GTX1080

I notice that leaving base clock, multiplier, etc. all alone/stock, performance is stable, not too bad. As I overclock this PC, in general operation things start to slow down or frequently pause. This is very evident with benchmarks... 3DMark scores drop to a third as my base rate goes from 3.4Ghz to 3.9Ghz for example. Similarly, games/etc. take longer to load, browser scrolling becomes somewhat stuttered and I start to miss frames in games. Under load the CPU appears stable when overclocked, and temperatures rise but the monitoring tools I'm using (cpu-z, various asus/evga tools) do not show any sudden high temps forcing the CPU to reduce speed. (Things rarely get above ~ 65C.) Perhaps it's happening and the monitoring tools don't pick up the swings?

My guess is that the heat sink isn't making good contact with the CPU, but before tearing things down I'd like to ask if others have seen this and can give me other potential root causes to check out.

I'm using a Corsair H100i closed loop water cooler for the CPU sink.

Might check windows' event log viewer to see if there are any WHEA errors, could be your overclock is unstable. Every error it has to correct reduces performance a little bit, similar to an unstable GPU overclock.

Thanks and good idea. I neglected to mention in my original post that there are no unusual messages in the event logs beyond the usual noise.

Are you using the BCLK to overclock and not JUST the multiplier? That can easily cause the slow downs that you describe - oiverclocking via BCLK overclocks the various buses which can cause the slow downs as the computer tries to correct errors.

Is your CPU overheating? Maybe your cooler can't keep up, maybe you left the CPU voltage to AUTO and it is applying too much voltage (causing too much heat + downclocking/slowdowns)?

is very easy to figure out whats going on....but you need to be able whats happening. Are your cpu clocks holding steady under stress? i recomend installing afterburner with riva tuner server osd so you can visually see whats happening during the performance drop. I bet you have bad cpu contact and is over heating before it throttles.

BLCK was held steady, the problem was occurring tweaking just the multiplier. I also tried rivatuner and did not see any unusual temperature spikes under load. So, I decided to bite the bullet, make a quick trip to Fry's (really love that aspect of relocating to California...) to get some TIM (MASSCOOL G751 Shin-Etsu Thermal Interface Material - Newegg.com) and viola, problem solved.

I'm guessing that there was throttling going on, but perhaps it was a thermistor in the die that doesn't report and is more sensitive? Or some other mechanism.

In either case, this thing is running *smooth* - 47x multiplier on 100Mhz BCLK. Very happy.

Never been to frys.....but i used to love driving by micro center in jersey. Probably one of the few occasions i enjoy shopping lol . Your theory regarding the temps seems reasonable, especially if its good now!