Core i7-8700k - needing 1.3v for 4.8ghz, 1.35 for 4.9ghz... worth delidding?

TerminatorUK

TerminatorUK

TerminatorUK

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Hi folks,

I hope you are well and can help provide your 2p worth on my 'situation' (well and truly in the realm of '1st world problems :))

I've recently built myself a Core i7-8700k system on an MSI Z379 Gaming M5 motherboard with 16GB of Corsair Vengeance RAM at 3000mhz 14-14-14-34 2T.

The system is placed inside of a Coolermaster HAF-X case and uses a Fractal Design Celsius S36 360mm AIO cooler.

Firstly I spent a while getting the RAM all mem-tested and 100% stable which I am now happy with after using memtest to get full coverage of the RAM overnight.

With that out of the way, I decided to use the hot weather in the UK to do a bit of 'worst case scenario' overclocking (hey what else would you do? ^_^) with my new i7-8700k.

I'm determined to hit 5ghz this time around (I have my heart set on it! :) after the success) and make a half decent gap from the system I have just come from was my faithful Core i7-4790k which I've been running stable at 4.5Ghz for several years.

Cutting to the chase, it seems that I might have received a bit of a lemon (not the absolute worst but not great either):

4.8Ghz requires 1.3v. Temps in Prime95 = 79-81oC

4.9Ghz requires 1.35v. Temps in Prime95 = 88-91oC

5Ghz requires 1.4v to boot. BSOD quickly in Prime95.

Not dared to go any further due to heat and approving TJMAX limit.

So my question is, is it worth me looking at the prospect of delidding the CPU to improve temperatures or am I better off looking to get another 8700k and re-roll the dice on the silicon lottery before looking at de-lidding?

Many thanks for your assistance / views in advance! :)
 
Really appreciate your replies folks - much appreciated.

Noted on the memory - very interesting and wouldn't have considered that causing the instability - I will keep that in mind.

I feel a little guilty that I've 'cheated' my way out here after seeing an excellent opportunity on the site which rhymes with eSleigh :-)

I've sold my 8700k now and awaiting delivery of another 8700k that has already been delidded and confirmed to hit 5ghz @ 1.36v at around 70oC during stress stressing with a Dark Rock 4 air cooler.

The venture has only cost me a delta of £40 and I'm a bit of a sucker for guarantees so this was too good of an opportunity to pass on.

I will post my results once it is planted into my system :-)
 
acemastr said:
You may find this gives you the same results if the memory clock isn't working right.

I must have won the silicon lottery as I'm sitting at 5ghz 1.3v without any issues.
I guess with that delta you've covered the cost of the delidding tool so it isn't such a bad deal!
Click to expand...

Exactly - the latter point was precisely what I was thinking and what pushed me this direction; the cost of all the materials / tools I'd need probably would have been that sort of price anyway.

The fact that the risk (albeit not massive) that the work has been done (successfully) already + they have achieved the figure I was after at an acceptable voltage to me was an opportunity I didn't want to pass on.
 
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Hi all - just to update this thread.

The new CPU arrived today (finally!) but hasn't been without some drama.

Firstly after seating, pasting and attaching the CPU block - the machine wouldn't post - DOA I thought - I've been had here!

I proceeded to reseat the CPU as I'm no over the moon with the condition of the pins on the motherboard so thought I'd give it try.

Lo and behold, it booted to Windows but I noticed the temps were 85oC idle - I've been had here, I thought!

No, no - like an idiot, I forgot to plug in the 4-pin fan/pump cable.

Sorted that - booted - 35oC idle....phew!

Stress testing....default settings about 50oC - very nice :-) Annoyingly one core (Core #0) is about 12oC hotter than the others for some reason.

Overclocking time....I'm in love I think :-) Running Prime95 at 5ghz, 69-71oC, 1.34v :-D - much better

Again though, Core #0 is around 83oC on the same test which is very frustrating

Going to wipe off the thermal paste between the IHS and the CPU block and try it again - the start of the new tube of MX-4 I was using was very watery and may have split when I re-seated the CPU; I'll try it and report back.

I'm hoping it isn't a bad job on the liquid metal between the CPU die and the underside of the IHS....
 
chrcoluk said:
delidding lowers temps, I have never heard of heat causing a BSOD on a cpu, so if you need 1.4v to boot 5ghz and it still isnt stable, I dont see how delidding is going to help you unless you prepared to run with insane voltages and the delid is just a way to prevent thermal throttling.
Click to expand...

Indeed - that's why I threw in the towel on The first CPU immediately sold up and bought and bought a 2nd one confirmed to hit 5ghz at a much lower voltage.

This second is massively better and seems to be Prime stable at 5ghz with 1.312v volts (certainly for 30 mins I've checked so far) with no modifications to the memory speed or timings in any way that I was using on the previous CPU.

Now I know the CPU is good (but the while delid quality is unknown to me) I think it is worth me investing into a further de-lid to check it out any ensure there isn't anything amiss (like liquid metal leaked onto any of the contacts) and it is making good contact with the IHS etc... as that is all an unknown to me because I didn't do it myself.

Thanks for the confirmation guys - confirmed my suspicions - I'll provide an update after the re de-lid work has been done.
 
LuckyBenski said:
Sounds good. Get every element set up perfect yourself!

TBF I would do longer prime testing than 30 minutes. But then for me 100% stable means "doesn't crash, ever" because that's how I want my machines to behave.
Click to expand...

I agree - 8 hours Prime stable is my benchmark.

Interestingly, I did get a crash after 4.5 hrs at 1.312v so looks like it wasn't quite enough voltage afterall.

Set off again at 1.320v this time...fairly round number. Been chugging nicely for 4 hours so far...

Temps are 69-71oC except for that damn core #0 at 83oC.

My pickiness and curiosity has gotten the better of me and i'm going for a re de-lid but, forgive me for thou has cheated again :-(

I've found a rather cheap pro service (same site) that'll do it for just over a tenner which is too hard to refuse (would cost me more in materials).

To answer your question chrcoluk, it only cost me £40 difference initally between my sale and buying the 2nd one, however, that's creaping up slightly going for the 2nd de-lid but that's only because I'm super picky and need to know the orginal job has been done properly (and don't want core #0 to 'burn out' faster than the others).

Stupid I know but taking care of my new precious :-P
 
LuckyBenski said:
Personally I'd buy the liquid metal and some epoxy for the same price, and you can redo it 5 times, do it for mates etc. Seems like you're the tweaking type. But then I'm a chronic DIYer and buy every tool...
Click to expand...

You're right and I tend to be as well and if I ever needed to do it again, I probably would buy the stuff next time
 
Good news folks - result!

Got my re de-lidded CPU back and it was well worth it - very neat job the guy did (sent me pictures) and I have peace of mind that the contacts near the CPU die have been varnished off.

The newly done CPU now sits at 70-75oC across the board in Prime95 so I'm very happy I took the gamble :D


5ghz_re-de-lid.png
 
CPU stabilises at around 76-77oC on Prime95 with Large FFT's stress testing.

So you could say I've gain a few degrees across the board but that might be a bad application of MX4 on the top of the IHS - not sure.

I'm still happy that all cores are around the same temperature and nothing is cooking itself in the mid-80oC region though so still pleased I got it done

I've got test running at the moment since 9am and I thought it had 'failed' at 9:30am (nearly went proper mad at some instability). Turned out that the PC has simply put itself to sleep after I reinstalled Windows last night and it has default to a 'balanced' power plan which puts itself to sleep after 30 mins! :D Will see if that lasts the day without crashing...

During gaming, temps across all cores was about 49oC so I was pretty happy with that :)
 
Final update - stress test with Large FFTs passed 8 hours with no crashes at 1.320v - happy with that results and branding it with the 'stable' overclocking stamp :-)

Time to actually put my CPU to use and enjoy it :-D
 
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