Maximum PC

I've read that the i7-2600K can easily reach 4.7-4.8 on air, and can even reach 5+ GHz with some additional tweaking. If so, then I must be doing something wrong.

I'm running a 2600K with a CM Hyper 212+ (with 2 2000RPM fans), Arctic MX-4 thermal paste, a Corsair TX650, Gigabyte Z68X-UD3H-B3 mobo, and a CM Storm Enforcer chassis with an extra exhaust fan on top.

I figured this CPU could do 4.6 easily, especially with the extra CPU fan. So I cranked the multiplier up to 46 right away. But 5 minutes into Prime95, it blue-screened. I don't know why; temps never got above 66-67°C. I now have it clocked at a safer 4.2, and it seems stable after a couple of hours of stress. Temps top out at 62°C.

So why am I not getting 4.8 like most people with this CPU? Do I need to play with voltages? Do I just have an unlucky part? I already re-seated the heatsink, so I doubt it's a thermal issue, especially since most users report no problems at 70-75°C.

I'd look at the voltages. not sure on specifics for sandy bridge though.





Ted

Okay. I'll try to search around and see what voltages are safe. I don't want to make a rookie mistake and fry my CPU.

Keep in mind that not all parts will overclock the same. When it comes to CPU's, the potential of identical parts can actually differ greatly. The two greatest variables are conductivity and heat production (the first is a strong influence on the latter).

I sincerely doubt that you got a bum chip, and don't go adding voltage until other possibilities have been properly addressed.

Changing the multiplier allows OC'ing without altering the core freq, which is important to Sandy Bridge chips because the memory controller, IGP, CPU, etc. are all tied together by one bus speed. The whole reason Intel released the K-series is because the new architecture is not stable when OC'ed via BCLK. This is significant because since you're not changing the bus your RAM speed should be unaltered, which effectively rules out the RAM as the culprit.

Changing the multiplier does however influence the QPI speed (Quick Path Interconnect). As you increase your CPU multipier you need to lower the multiplier of the QPI to keep it within reasonable limits. The number of multipliers available to adjust the QPI will differ depending on what BIOS or UEFI your board uses. Check the initial speed at stock settings, and stay as close as you can to that while you are overclocking the CPU. Obviously the QPI will be running at faster than rated speed when all is said and done, but the closer you can stay to that stock speed, the more stable and cooler your CPU will run.

Good luck.

So, I bumped the voltage up to 1.38 V. Based on what I've read around the internet, anything at about 1.4 V or less is ideal for everyday use.

Sadly, nothing has changed. Anything over 4.5 still blue-screens almost instantly (in Prime95). I'll run Prime95 overnight at 4.5 and see what happens.

I can't seem to find any sort of QPI multiplier. I see QPI voltage, but nothing else references QPI. I'll look again, though.

Thanks for the replies! Even if I can't get past 4.2 stable, I've still got a screaming fast proc.

EDIT: And it's not a thermal issue. I haven't even hit 70°C yet.

EDIT: Blue-Screened 4 hours in at 4.5. Ugh. Let's hope 4.4 is stable.

Are there any settings I should be disabling or changing in the BIOS when I overclock?

Run CPU-Z and check your QPI speed. There has to be something in the BIOS that will allow you to run the QPI at a lower multiplier. I can almost guarantee that's your issue, but CPU-Z will confirm. Your motherboard manual may have a section covering the BIOS, or UEFI.

Okay, it survived Prime95 for 6 hours at 4.4 with Vcore at 1.35 V (I would have run it longer but my power cut out momentarily). I'm gonna assume it's stable.


I just did some Google searching and found that Sandy Bridge CPUs don't use QPI because the northbridge is integrated with the CPU. I guess that eliminates that option.

Put your Load Line Calibration at ultra High,
Your CPU current capability at 130,
Put your VRM at 350 to 360,
The Digi+ VRM Phase Control should be at Optimized,
DRM+ VRM Duty control should be set to extreme.
Also keep your voltage at about 1.38 to 1.4
hope this helps

Ugh... Why isn't any of this stuff in the BIOS? Is it all under different names or something? Do Gigabyte boards just have crappy BIOS settings? I don't see anything that resembles LLC or Digi+ VRM controls.

I'm almost ready to give up and just stay under 4.4.

Shit, Yeah they would be under different names... Im not too sure about gigabyte boards.

Here's what I see under Advanced CPU Core Features:



And here's what's under Advanced Voltage Settings (everything CPU-related):
EDIT: Options under Multi-Step Load-Line are Levels 1-10. Does anyone know what Load-Line Calibration values these match?

WOW!!! Ummmm... They are completely different... Hmmm, This is why I do ASUS, they are so much more user friendly, and IMO a better company to go with when it comes to computer hardware. Wish I could be of better assistance... Sorry

It's alright; can't do anything about that.

Well, some additional Google searches really helped. I now have the Load-Line set to Level 6 and I no longer get instant Blue screens at 4.6! That must be equal to vDroop/LLC.

It's a learning process for sure.

Ah yes. Appears that only the soon to arrive 3820 and above will use QPI...

http://en.wikipedia.org/wiki/Sandy_Bridge

Sucks for 2000 series owners.

In addition, with Load Line Calibration disabled, the CPU should run at Intel spec.