Haswell Heat

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|DFA| Havoc

Limp Gawd
Joined
Aug 4, 2014
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203
So I've built, I dunno, probably close to a dozen systems with Haswell / Devil's Canyon i7s, and lately I've been having trouble with chips that just run blazing hot under load.

The first of these chips was a 4770k that I had under an H100i that would spike up to 100c immediately under Prime95 small FFTs. I re-applied the thermal compound 3 times, tried all kinds of different settings for the cooler, including permanent 100% fan speed, nothing made a difference. I thought the cooler was at fault, bad pump or uneven coldplate or something, replaced it with a new one and same thing. In the end the only thing that worked was undervolting, which I've never had to do to get a chip to just run at stock speeds before.

I've got a 4790k now which is exhibiting similar behavior, and I'm pretty miffed. I'm not overclocking these suckers, just trying to get them to run at factory clocks without melting down. I've tried all kinds of different coolers and thermal compound, nothing seems to help.

Is undervolting the only solution short of delidding and thereby voiding the warranty? :/
 
Test using a different program.

The newest versions of Prime95 will utilize Haswell's AVX2 extensions, this also causes the CPU to increase vcore via an internal offset.
 
For the 4770K + 100i:
The block probably isn't making good contact with the IHS. If you're working with an incorrectly installed backplate or a thin motherboard, no amount of reapplying thermal compound with help. You're going to need to check if you have the backplate installed correctly, and also if you need some spacers/washers installed to close the gap.

I don't know what is causing the high temperatures in your other setups.
 
It is AVX2, which newer versions of Prime95 use. It is dangerous to use in that manner, and should not be used with haswell or newer chips, overclocked or not. AVX2 has been known to cause chips to throttle even at stock speeds, due to the extreme current draw it causes.

Try this version of Prime95, which is the last version not to use AVX2:

http://www.mersenneforum.org/showthread.php?t=15504
 
I also thought it was the block on the h100i at fault, so I sent it back to Corsair for replacement, and the new one behaved almost identically. :/

As for Prime95, I've been using the same version to test on all my Haswell builds, and previous runs haven't been quite this bad, so I'm hesitant to blame it all on the AVX2 instructions.
 
|DFA| Havoc said:
As for Prime95, I've been using the same version to test on all my Haswell builds, and previous runs haven't been quite this bad, so I'm hesitant to blame it all on the AVX2 instructions.
Click to expand...

What version are you using? Follow the link above, download 26.6 which is the last version without AVX2, try both and compare your results. Since that is essentially the only major difference, if you see different temps, then the reason is obvious. If temps are the same, then it's something else. This is a very simple test. It doesn't have to be a guessing game, unless you prefer it that way.
 
I have a 4790k with a H105 (thicker rad than H100) and never see much above 50c while gaming. (Arctic Silver paste). It's at stock clocks forced to run at 100% (no step down) so it's always at 4200-4400mhz.

I don't really see the point in torture tests as it performs great in my real-world usage so that's all I care about.
 
|DFA| Havoc said:
I also thought it was the block on the h100i at fault, so I sent it back to Corsair for replacement, and the new one behaved almost identically. :/

As for Prime95, I've been using the same version to test on all my Haswell builds, and previous runs haven't been quite this bad, so I'm hesitant to blame it all on the AVX2 instructions.
Click to expand...

It's not the block, it's the gap.
 
Suprfire said:
It's not the block, it's the gap.
Click to expand...

Sorry, I guess I had just skimmed through your reply the first time I read it. After re-reading I decided to double check and make sure that wasn't the issue with the current chip. I tried tightening the mounting posts a bit - nothing crazy - and the one on the bottom right actually chewed right into the surface of the motherboard and damaged the traces connecting to the first two RAM slots, which no longer function. So that's awesome I guess.

I ended up buying a new motherboard, and just finished putting the system back together. It looks like the motherboard is putting slightly less (.05) voltage through the chip under full load at stock settings, and prime95 is now stabilizing in the 85c range on the two hottest cores. Just out of curiosity, I also tried running version 26.6 as suggested, and the results are pretty much the same as the version that I've been using (28.5), maybe 1-2c difference at most.

I'll settle for low-mid 80s under prime95, I just wish it hadn't cost me a motherboard to get there. :|
 
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