Question Some Cores of my i7 8700k died and I'm wondering if I'm the cause.

[Slayer418]

I will share one of my reddit post on the matter so you can know the whole story : View: https://www.reddit.com/r/techsupport/comments/cehmqz/could_a_security_leak_on_my_system_allows_a/

(if this practice isn't appreciated here, I will post a tldr).

I posted it few days ago and it didnt get much attention but it's whatever since now I just went back on reading about how to properly OC and while I never went crazy on my OC ( 4.4GHz all cores with my 8700k), I think I may have did something really bad after I updated my BIOS (which was few days before my CPU go bad). I was restoring settings from what I could remember since the backup file couldn't be used (...) when I decided to up my clock to 4.7 from the 4.4 I've had always been using. I then started to do some testing with manual voltage but I finally left it on auto because it seemed fine. Here come the mistake, I arrived to the LLC setting which I'd always set to max in the past because I read about it being a good thing to do to ensure stability back when I had a 4790k. What I forgot I guess is that I would use manual voltage with such extreme LLC.

I won't lie, I didnt check my voltage on full load while gaming after applying these changes (stupidity at plain sight right there). I know it was @ 1.2 - 1.25v on idle.
So could these settings set that way have killed some cores before even showing signs of something being not OK?

 

[CompuTronix]

Slayer418,

I see this is only your second post on our forums since 2015 ... I hope that your first experience was positive.

That's an ugly problem you've described. It certainly leaves a lot of room for speculation.

• You haven't mentioned whether you've ruled out Windows by running a fresh load from a different drive that's a known good drive?

Although Intel's datasheets specify a maximum value of 1.52, Vcore is nominal up to 1.45 under 100% workload. However, it's not recommended to run above 1.4 for daily use on 14 nanometer processors.

LLC is designed to compensate for "Vdroop" when heavy loads can cause Vcore to significantly decrease. When set correctly, Vcore should remain relatively constant (within 25 millivolts or less) during heavy loads, rather than "drooping" which can cause BSOD crashes. If LLC is set too high, then heavy loads can cause Vcore to "spike" well above its BIOS setting, which can be potentially damaging to the processor. So the objective is to set LLC to maintain Vcore at constant values during light and heavy loads, favoring a slight droop in preference to spiking, which typically does not mean "max".

If you're unaware of the actual Vcore during heavy loads prior to the failure, then we can't rule out the possibility of damage due to excessive Vcore.

Just as you suspect, it's also plausible the damage could've occurred during your main input power fluctuations. There are many types of distinct but damaging power anomalies that can come down the line and you'll never see the lights flicker. General sags and surges are just the tip of the iceberg. Power anomalies can also come across neutral as well as ground, rather than only phase, which is especially true during thunderstorms and nearby lightning strikes.

Surge protectors or power strips with surge "protection" are rated in "Joules", so the higher the value the better. UPSs also have surge protection features, some of which are excellent. In addition to sustaining line input power to you computer's PSU during brownouts or total outages, a good UPS will filter out most or significantly reduce the severity of power anomalies.

Unfortunately, a power spike could've passed through the PSU and damaged the VRMs on your previous motherboard, which combined with max LLC, could've damaged your 8700K. Regardless, the nature of the problem you've described at least "suggests" that your processor's microcode has been corrupted, and / or has suffered nanocircuit damage within the die relative to uncore components on the ring bus.

However, before you roll the dice and drop your hard earned dough on a pricey replacement processor, just for test purposes, you might want to consider ordering a Celeron G4900 from eBay for $40.00. The G4900 is listed as a supported processor on Asus's website for your Z390F Gaming.

CT

 

[Slayer418]

Oh I already ordered a 9700k since I'm sure the CPU was the problem.

My 8700k is still working ( as in it doesnt bsod anymore and I can even play Path of Exile, with massive performance dropout that is) but only when I disable all but 1 core (can't figure out which cores are dead but even if I could, it's not possible anymore to disable specific cores only).

I will probably RMA it but I'd like to be sure I'm not responsible of what happened thus voiding the warranty.


Like would it be possible that the Vcore, while being on auto and with LLC set to 9 (highest on Asus MB) would go as high as 1.5v? I will probably test it in few hours when I get off work.

And to reply about this being my second post here after several years, it's mainly due to the fact that I rarely face any issues that requires me to ask for help. I never really had hardware issues over 15 years and multiple rigs. I usually succeed to fix my software issues because I can use google ( no joke, it's probably one of the important skill to have for solving issues, I'm surely level 100 googler).

 

[CompuTronix]

Depending on BIOS versions, some Z3xx motherboards on auto Vcore have been known to exceed 1.5, regardless of LLC, thereby killing the processor.

 

[Slayer418]

So in such case is the CPU still covered by the warranty?

 

[CompuTronix]

That depends on the retailer and Intel ... and what information you volunteer.

 

[Slayer418]

Hmm they can't really know what happened either is what you're trying to say so if I don't specify having done certain things, it should be fine?

 

[CompuTronix]

8700K failed to boot. Motherboard replaced, still failed to boot. 9700K boots OK. Enough said.

 

[Slayer418]

Ok just did some testing, I set LLC back to 7 (which is the highest on z390, I swear it was 9 on z370 but maybe I'm wrong), disabled MCE, set the single core to 47x and left Vcore on auto.

Lowest Vcore being reported by HWInfo is 1.26 and I see alot of spikes to 1.3

https://imgur.com/ipMVEPq

View: https://i.imgur.com/ipMVEPq.png



I don't know if it's a reliable test, I played for a few minutes (which was, of course, using my only core to 100%) but I feel like LLC isn't what broke my CPU.

I definitely don't like having my voltage spikes so much tho, I will need to tweak things.

 

[CompuTronix]

Regardless of LLC, without having laboratory grade power monitoring equipment connected to all AC and DC inputs and outputs using the previous motherboard, it's pointless to speculate any further, as there's no way to duplicate those power fluctuation events to know what actually happened. I would purchase a good UPS, drop in your 9700K and chalk it all up to experience.

 

[Slayer418]

I received my 9700k and everything is working perfectly. I set it to 4.6Ghz @ 1.175v (lower than that would cause WATCHDOG BSOD) with LLC 5 (with of course all power saving off). On idle my vcore is at 1.163 and on load it vdroops to 1.146. On a 20min AIDA64 Stability Test, temp was at about 70C towards the end.

Oh and also, I already bought a nice UPS. It gives me about 20min autonomy on load which is whatever anyways because it's main use is to just avoid computer shutting down abruptly and the overshoot of the current coming back.

Now that my hardware issue is finally fixed, back to trying to maximize performance in Windows .
I want to get the most stable FPS possible and as close to 144 as possible (gaming on 1440p is hard). Since i had alot of time those past few weeks, I read alot on the matter (once again but even deeper) and found some interesting tips.
For example, I wanted to dedicate some cores to a game while the remaining cores would be for background/systems processes. I've yet to test this and see if this would have the possitive impact on performance I'm looking for but during my googling, I found a reddit post talking about Disabling Core 0 (which would be used by alot of system processes) for your games could increase performance or atleast the stability (higher min FPS, get rid of stutter etc..). I tested this trick (only with Path of Exile so far) and it seemed to have a noticeable possitive impact but I'll need to conduct more test on different games to see how good it is.


There is one thing that I really want to fix tho and so far nothing worked, my DWM uses alot of GPU (sometimes 40%) while I'm gaming (I always play in Borderless because I alt-tab alot but even in Exclusive Fullscreen, DWM still uses the GPU. I remember not having such issues on Win10 1608 and it started only when I upgraded to 1809 a couple months ago.

I read about forcing DWM onto the integrated GPU (using Windows Advanced Graphic Settings) which I tried to accomplish but the process is sticking to my 1080 for some reason. I also read about Nvidia Optimus but it doesn't seem to be enabled on my rig (maybe it's for Laptop only) and now I'm searching a way to force enable it.