Z77A-GD65 + i5 2500K Overclocking - How to start?

[Zach_]

Well, yeah, that could be an option :)

Aaaaaanyway, well, after increasing to 1.4, I'm seeing more stability on Prime, passed the first 400K AVX FFT and now on another 128K AVX FFT test, it's been testing for 20 minutes and no BSOD, so looks like it may have been the Vcore, but of course, I'll only know in a few hours.

I'm stressing large FFTs now, after hopefully completing, I'll move on to small FFTs and then Blend

I guess you're right, you gotta test for stability as much as you can.

To be honest, I didn't do any stress or stability testing when I first built the system, I tend to rely on components when they run at their stock speeds, I just don't have the energy for it :)

[profJim]

Overclocking is like racing, how fast are you willing to spend....
....money
....effort

[Zach_]

Yeah yeah I know :D

Anyway, how far would you push the Vcore on the 2500K? I know that Intel says max safe voltage is 1.52 but is it really? The Gurus as MSI said that they prefer not to cross 1.4, what do you think Jim?

Can you also please explain how Prime95 AVX is different than the regular Prime95? Chike said that it uses double the memory, but I'm running large FFTs now and only 1.3GB is being used.

[profJim]

Your cpu won't live as long with high voltages, but what does this really mean?
Will your cpu only last 5 years instead of 10 years?
Are you willing to upgrade your cpu cooling to run at higher speeds.
From my Core2Duo overclocking, I found that for a 10% speed increase, benchmarks improved 5%, half the amount, but real world performance increases often weren't really noticeable. To me, it boils down to how much better your games and programs run at higher speeds.

In general, if Intel's max cpu voltage is 1.52 volts using air or water cooling, I'd be comfortable at that voltage, and possibly up to 10% higher.
But I'd like to know how and why the "experts" say to keep it at 1.4 volts.
I think that their 1.4 volt recommendation is for Ivy Bridge cpu's, and not for Sandy Bridge.
Ivy Bridge seems to go bananas heat wise above 1.4 volts.

[Chike]

Now don't twist my words, I said double the memory access. The AVX can do x2 operations per clock and thus increases memory bandwidth, which is of course putting more stress on the "I/O".

[Zach_]

Your cpu won't live as long with high voltages, but what does this really mean?
Will your cpu only last 5 years instead of 10 years?
Are you willing to upgrade your cpu cooling to run at higher speeds.
From my Core2Duo overclocking, I found that for a 10% speed increase, benchmarks improved 5%, half the amount, but real world performance increases often weren't really noticeable. To me, it boils down to how much better your games and programs run at higher speeds.

In general, if Intel's max cpu voltage is 1.52 volts using air or water cooling, I'd be comfortable at that voltage, and possibly up to 10% higher.
But I'd like to know how and why the "experts" say to keep it at 1.4 volts.
I think that their 1.4 volt recommendation is for Ivy Bridge cpu's, and not for Sandy Bridge.
Ivy Bridge seems to go bananas heat wise above 1.4 volts.

I don't think he was referring to Ivy since the dude runs 2 Sandys at very high clocks of over 5GHz, 2600K and 2700K, here's what he said:

Always best to check the Intel datasheets for both the CPU series 'and' the chipset. Intel changed how they list some CPU voltages as of late. They give absolute max. VCore instead of the industry recommended max. of a 1.400v. limit. It is highly recommended to not exceed that for an everyday use type machine. On any given day, components are getting swapped out on a number of rigs. Makes life interesting. One week will run Turbo OC, the next a CPU Ratio OC, the next a raw OC with no power saving enabled. I do maintain the 1.400v. limit though (except for any extreme OC runs of course). You are on the right track. Trial and error within the specs is the best advice I could give you.

Basically he says that 1.52 is the absolute max Vcore (Meltdown point?) and that the industry safe voltage is 1.4
Your thoughts?

I'm willing to plunk down another 50-70USD for a better cooling solution if need be but honestly, except for the CNPS10X Extreme being a bit noisy, I think it performs really well, keeps my temps at or below 70C at max stress, if there's a need to upgrade it, do tell :)

Now about Prime, looks like Vcore was the issue, I've been running a large FFT test with Vcore 1.4 for exactly an hour and it seems stable, hopefully it will complete 8-10 hours of large FFTs and then I'll move to small FFTs.

Now don't twist my words, I said double the memory access. The AVX can do x2 operations per clock and thus increases memory bandwidth, which is of course putting more stress on the "I/O".

Oh sorry Chike, I thought you meant double usage of memory. Don't get mad :) :) :)

[Chike]

I don't know who gives this guy his information, but in Intel SB datasheet the VID range for the CPU is 0.something to 1.52v max (never said absolute).
Both I/O and SA voltages exceed their "max" by overclockers, question is how lucky do you feel.

[profJim]

A web search using: i5-2500k maximum voltage provides quite a few differing opinions.
With decent cooling, up to 1.42 volts is probably safe for gaming or when maximum performance is needed.
I suggest going with two different stable bios profiles, one for 24/7 "normal" operation and one for gaming.

If I had your setup, I would measure cpu voltages with a DMM with different LLC settings.
Maybe the MSI LLC setup isn't that great.
In Sin's z77/IB review with a Gigabyte board, I think he recommended the Turbo LLC setting, and not to use the Extreme LLC setting.

With older LGA775 setups, enabling LLC would let you run with slightly lower cpu voltages.

[Zach_]

yeah I read that too but I thought 1.52 is the absolute voltage, I've also read a review in which I remember the reviewer writing that 1.4 is nothing for Sandy Bridge CPUs but it's a lot for Ivys...

Well, in that case, 4.8 might be an option :)

So far my large FFT test is running for 2 hours and looking good.

More updates to follow.

[profJim]

More updates to follow.

Thanks for the warning