Very strange problem overclocking my GTX 480?

[systemlord]

Alright I'm having a very strange problem overclocking my GTX 480, I started overclocking on Thursday and I reached 870MHz core stable (1.138V) using EVGA OC Scanner and OCCT for several hours on each, then on Friday I noticed a loud buzzing sound coming from around the mosfets/chokes/VRM area. So I thought that I should decrease it to 850MHz where I've had it since March with no issues, except the buzzing sound was still there. All three days "Unlock Power Draw" was checked!

So I decided to decreased it all the way to 720MHz and the buzzing sound was stiil there, so I gave up for the day. Today Saturday I started all over again and eventually reached 880MHz core (1.138V) with no buzzing sounds and it was rock solid stable at 880MHz core and I even let EVGA OC Scanner finish on its own almost 2 hours later without any errors or artifacts. Temperatures were very consistent all three days, what in the world is going on here?

 

[Tamz_msc]

What PSU have you got?

 

[abswindows7]

May be the buzzing sound was a timer for the eggs you are trying to cook on your hot card

 

[abswindows7]

Just kididng.

It's weird, if it continues, you'll have to rma the card ...

 

[systemlord]

I have reached an incredible 905MHz Core, 1810MHz Shader and 4400MHz Memory @1.2V 52C loaded! I have run OC Scanner for several hours with no errors and OCCT has also produced no errors! When I had all of my problems I was using Nvidia Inspector , since I change to MSI's newest version of Afterburner the buzzing/problems disappeared and OC limits exceeded my wildest expectations! EVGA's OC Scanner (79% GPU usage) does not fully stress my card like Furmark does use 99% GPU usage, is GPU usage the same thing as GPU load? There is absolutely NO buzzing anymore, just a quiet heavily OC'ed card!

 

[Tamz_msc]

GPU usage is the same as GPU load.

 

[systemlord]

Lastnight I discovered something, if I OC my 480 to 905MHz core, 1810 shader and 4400MHz memory with Vsync Forced "On" I'm rock solid stable. If I Force Vsync "Off" I'm getting errors left and right with my GPU load at 100% and with Vsync "On" my GPU load is only 70%.