I7 875k Overclocking Wall

Got a new system put together and trying to really make it stretch out.

The meat and bones of it are:
i7 875k
Gigabyte UD4P
Mushkin Ridgeback 1600 CL6 2x2 GB 1.65v
MSI Hawk Talon Attack
HAF X Tower
Thermalright Silver Arrow w/ 3 Fans
1050W ABS PS

Seems to overclock very easily to about 4.125 Ghz with energy saver features disabled and Vdroop enabled. Just adjust the multiplier. Hyperthreading enabled.

http://img10.imageshack.us/img10/172/auto31m.th.gif" class="img lazy">

Temperatures seem very reasonable.

Once I start pushing 4.2+ and adjusting the voltages to get some stability temperatures just start exploding.

http://img600.imageshack.us/img600/6421/12289038.th.gif" class="img lazy">

http://img130.imageshack.us/img130/1039/4320ghz138v.th.gif" class="img lazy">

Temperatures are nuts in this last one and it was only stable for 8 passes. Missed a screenshot at some point here. But I made 8 passes at about 53.5 Gflops. System didn't crash just said I was unstable. Voltage is about 1.382 on this last one and shows stable at about 1.402 in CPUZ.

Is this a bad chip? Should I remount my heatsink? Any feature I don't know about that I can adjust to increase stability at lower voltages?


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More about 875k overclocking wall
  1. 4ghz tends to be the wall. The K series is just nice because of the unlocked multipliers, but it doesn't mean it can get higher OCs other than it's not Baseclock-bound.

    You should disable Vdroop (aka enable load line calibration) since you disabled turbo. I found Vdroop is only good for a turbo--enabled OC because then it'll use different voltages at different speeds/multipliers. Since you're only running one multiplier, it only needs one voltage, and having LLC on might help with stability and definitely lower the voltage (although running voltage will be similar).

    Temps will skyrocket when the heat sink's cooling capacity is reached... a heat sink can only dissipate so many watts of heat energy per second. If possibly add a second fan, otherwise you'll need to go liquid cooling.

    Hyperthreading also puts a lot more stress on the CPU. If you disable that your temps and voltage should drop, and maybe then you can push 4.2-4.3ghz.

    Other than that, I'm curious why you have your baseclock at 133? Faster bclk = faster QPI. Also I don't know if your RAM multipliers are unlocked or what the options are, but 133 would have a tough time making 1600mhz. 160x10 would be much easier.
  2. Wolfram 23,

    I do have LLC enabled I keep calling it something different because my motherboard calls it Vdroop. Regarding the ram it's acctually running at 6-8-6-24 @ 1728Mhz. If I'm really pushing it I've toned it down. But I think you are absolutley right that my heatsink is just at the limit. I'm currently doing a review of the Noctua DH-14 and Silver Arrow in the coolers and heatsinks forum. The Noctua will arrive today. I'll see if I have any better luck with that.


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