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

Discussion in 'Overclocking & Cooling' started by TerminatorUK, 23 Jul 2018.

  1. TerminatorUK

    Gangster

    Joined: 19 Feb 2007

    Posts: 282

    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! :)
     
  2. acemastr

    Mobster

    Joined: 29 May 2010

    Posts: 4,713

    Location: Tampa, Florida

    Always worth delidding, will take 15-20c off.

    Bringing the temps down may make it more stable at 5ghz too. I'd try putting the RAM back to stock and overclock the cpu by itself too to see if you get any better results.
     
  3. LuckyBenski

    Mobster

    Joined: 28 Dec 2017

    Posts: 4,823

    Location: London

    Totally agree about the RAM, too high an overclock can reduce both stability and performance i.e. will reduce your maximum CPU overclock.

    I don't think a delid will always net you 10-20+ degrees but it seems the 8700k does consistently improve after being cracked open. It seems Haswell was a bit more "if it needs it".

    I'd delid, and decide from there - IMO should add resale value rather than reduce, as you'd likely be selling it on to an overclocker.
     
  4. tyler_jrb

    Mobster

    Joined: 24 Aug 2013

    Posts: 4,312

    Location: Lincolnshire

    Completely up to you, its always worth it just to bring the temps down.

    My chip is pretty mediocre as it requires 1.425v for 5.1ghz which it currently is at and is also delidded.

    Could probably bring it down but wheres the fun in that :p.

    [​IMG]
     
  5. TerminatorUK

    Gangster

    Joined: 19 Feb 2007

    Posts: 282

    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 :)
     
  6. acemastr

    Mobster

    Joined: 29 May 2010

    Posts: 4,713

    Location: Tampa, Florida

    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!
     
  7. TerminatorUK

    Gangster

    Joined: 19 Feb 2007

    Posts: 282

    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.
     
    Last edited: 25 Jul 2018
  8. TerminatorUK

    Gangster

    Joined: 19 Feb 2007

    Posts: 282

    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....
     
  9. TerminatorUK

    Gangster

    Joined: 19 Feb 2007

    Posts: 282

    Hmmm didn't help - pesky core #0 still running hotter. The delta seems even worse in games most cores are in the 45oC region....Core #0 is more like 60-65oC :-(
     
  10. LuckyBenski

    Mobster

    Joined: 28 Dec 2017

    Posts: 4,823

    Location: London

    Sounds like the liquid metal under the IHS could be redone. This is why I just tack it back on, so it's easy to re-delid.
     
  11. acemastr

    Mobster

    Joined: 29 May 2010

    Posts: 4,713

    Location: Tampa, Florida

    Yeah, I had the same when I delidded the first time, the IHS isn't making good contact with the die. It needs liquid metal re-doing.
    My issue was not removing all of the glue.
     
  12. chrcoluk

    Soldato

    Joined: 27 Feb 2015

    Posts: 5,386

    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.
     
  13. TerminatorUK

    Gangster

    Joined: 19 Feb 2007

    Posts: 282

    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.
     
  14. LuckyBenski

    Mobster

    Joined: 28 Dec 2017

    Posts: 4,823

    Location: London

    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.
     
  15. chrcoluk

    Soldato

    Joined: 27 Feb 2015

    Posts: 5,386

    yeah that 2nd cpu is mighty, how much did you lose out on to sell and buy a new cpu?
     
  16. TerminatorUK

    Gangster

    Joined: 19 Feb 2007

    Posts: 282

    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
     
  17. LuckyBenski

    Mobster

    Joined: 28 Dec 2017

    Posts: 4,823

    Location: London

    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...
     
  18. doyll

    Sgarrista

    Joined: 1 Jul 2011

    Posts: 8,281

    I'm not up on de-lidding. What is epoxy for?
     
  19. acemastr

    Mobster

    Joined: 29 May 2010

    Posts: 4,713

    Location: Tampa, Florida

    Re-attaching the IHS. Gasket sealant works well too, I used that.
     
  20. doyll

    Sgarrista

    Joined: 1 Jul 2011

    Posts: 8,281

    I've only done a few delids, but I used just a spot of super glue in 2 opposing corners. That way if you want to take if off again a little acetone or fingernail polish remover will easily dissolve it so IHS can be removed easily. ;)