My understanding with degradation is it depends on the Amperage you push through the CPU more than the voltage, the voltage only serves to enable a higher Amperage draw for a given workload. High amperage flooding down fine circuit traces wear them out through a process called electromigration. This process is accelerated by temperature (hence why the mantra of keeping the temps under control while overclocking) and finer manufacturing processes. Intel's latest 8700K is rated for 138A which translates to 186W of safe continuous operation at the typical 1.35V which Intel is willing to stand-by. The higher your voltage, the lower your power draw must be to reduce the amperage going through the CPU circuit. This means you either use less stressful applications on the CPU that won't force high power draws, use the CPU less often to minimize the time it spends at/beyond 138A or use a lower voltage (and potentially clockspeed).

My interpretation of Intel's 1.55V specification is that is the highest voltage allowed in a transient spike scenario. Overly high voltages can have to potential to cause damage to the CPU circuits by literally punching holes in things or arcing current across junctions/traces. In this context, the 1.35V maximum overclock voltage makes a lot of sense. Depending on the stability of the VRM, switching frequency and Vdroop allowed (which is typically .1V on most Intel CPUs by default), it doesn't take much to see that 1.35V can potentially spike to 1.45V without vdroop under load. This leaves a healthy .1V from 1.45V to the maximum limit for transient spikes which the VRMs didn't compensate for. With better mobos with more potent voltage controllers and VRMs I would imagine it would be safer to skirt the limit to 1.4V or higher.

 

Temperature is the main factor in electromigration. Voltage plays the second most important role because of higher potential energy overcoming the resistance in the circuit (current literally jumps between adjacent traces).

 

Disclaimer: The following experiment can merely guess the short/midterm voltage induced degradation and only the voltage induced degradation of 14 nm Intel CPUs at room temperature with air cooling. It does not reflect the combined degradation mechanism resulting from electromigration and temperature induced effects.

I'd refrain from dialing in 1.55 V as you'll most likely have to add another 10 mV or so to keep your super tight overclock stable within two weeks. Let me explain the experiment I've been doing for the past weeks before bothering you with numbers and details. I was about to start a dedicated thread to it but when I saw this one on the first page I thought that's the perfect place and timing.

So I had a few dud 7700Ks lying around which I decided to sacrifice for the sake of science I was really curious about the rate of degradation in new generation CPUs at crazy high voltages. One by one, I tested them to determine the amount of time (under constant high core voltage) it takes to see a noticeable change (which is 5 mV or 0.005 V) in the Vcore one needs to apply to stabilise a mediocre, rather low voltage overclock. My procedure follows as such:

First, I determined a very tight overclock and two corresponding core voltages namely Vcore_max_unstable and Vcore_min_stable. As the names suggest, there happens to be a rather sharp transition point in Vcore, below which I can repeatedly prove the overclock is unstable and above which it can repeatedly pass the stability test (that is the Vcore_min_stable) when using V-Ray benchmark which is a miraculously effective tool to roughly check the stability in a very quick fashion. Since the chips were dud and I intended to isolate the influence of other factors like current and temperature on degradation, I've set the fixed overclock speed for my experiment to 4.6 GHz. Here are the initial voltages for the following CPUs:

CPU1 (batch L709C966):
Vcore_max_unstable = 1.195 V
Vcore_min_stable = 1.200 V

CPU2 (batch L710C662):
Vcore_max_unstable = 1.175 V
Vcore_min_stable = 1.180 V

CPU3 (batch L709C966):
Vcore_max_unstable = 1.190 V
Vcore_min_stable = 1.195 V

Now it's time to apply those crazy voltages. Degrading new generation Intel chips wasn't really a distant concept to me as I'd already played with and completely degraded (complete degradation would mean the required minimum voltage gets shifted so much that it fails to boot even at its stock speed on a fresh motherboard) numerous CPUs before like several G4400s, many i3s and some i5 6400s so I already knew what to expect and that anything between 1.75-1.85 V could bring sudden death. That's why I limited myself to 1.7 V. But first I started with 1.55 V. I dialed it in, got to the Win10 desktop and simply waited. I didn't run any intentional tasks but only some background Windows processes were running. I just interrupted the experiment every 12 hours to check the stability at those low voltages I mentioned above. At first I thought it would take weeks to see any change in my stable min. Vcore but then I was surprised to witness that all 3 chips were unstable at the initially stable voltages after 36 hours. Here are the results of the 1.55 V experiment:

CPU1: new Vcore_min_stable = 1.205 V after 24 hours
CPU2: new Vcore_min_stable = 1.185 V after 36 hours
CPU3: new Vcore_min_stable = 1.200 V after 24 hours

Next up was 1.6 V. I checked the stability every 4 hours during the experiment which yielded:

CPU1: new Vcore_min_stable = 1.210 V after 8 hours
CPU2: new Vcore_min_stable = 1.190 V after 12 hours
CPU3: new Vcore_min_stable = 1.205 V after 12 hours

Then I went on to 1.65 V and checked the stability every half an hour

CPU1: new Vcore_min_stable = 1.215 V after 1 hour
CPU2: new Vcore_min_stable = 1.195 V after 1.5 hours
CPU3: new Vcore_min_stable = 1.210 V after 1 hour

Finally 1.7 V. I guess I didn't check the stability frequent enough but the outcome was still obvious

CPU1: new Vcore_min_stable = 1.220 V after 15 mins
CPU2: new Vcore_min_stable = 1.200 V after 30 mins
CPU3: new Vcore_min_stable = 1.215 V after 15 mins

Well, can we deduce anything from all that? I guess so. Just like the mean time to failure rates of silicon chips vs. temperature follow the Arrhenius curve (failure time decreases exponentially with increasing temperature), the degradation rate vs. core voltage could also be an exponential function as the activation energy for voltage induced degradation/breakdown depends on the electric field strength in the transistor. As a matter of fact, even those very roughly determined degradation rates in my experiment follow a very clear exponential trajectory as you can see below.

So I took the liberty to extrapolate it further into the lower voltages to predict the time it would take for the required min. stable Vcore to degrade by 5 mV. Of course I'm not suggesting that at 1.45 V your CPU will degrade by 5 mV after 1000 hours since there must be significant amount of uncertainty margin in this tiny experiment but at least it gives some abstract picture. Assuming the uncertainty is less than 10x I can pretty much say that you're sure to lose a very tight overclock after a year or so (10000 hours) if you set a 24/7 fixed Vcore of 1.45 but then again, it's only 0.005 Volts. Then if I assume that the amount of voltage shift degradation has also an exponential behaviour, I can predict another trajectory namely the 50 mV degradation curve. What this curve shows at 1.5 V is particularly interesting to me as it would suggest the stable Vcore to shift by 50 mV after about 20000 hours which is 2.5 years. Given that Intel insists on the absolute max. voltage rating of 1.52 V for 3 years of warranty, the prediction doesn't seem too far fetched. And I also think Intel sets the stock VID to around 50-100 mV higher than what the chip can actually remain stable. Considering the 7700K I think every single chip can operate stable below 1.2 V at a stock turbo of 4.5 GHz but the stock voltage for it seems to be around 1.25-1.27 V. Which means even if you push your chip to the limits for 2.5 years with a constant 1.5 V, Intel has to make sure it's still stable at 1.25 V.

Then what's the bottom line? To me, the bottom line is unless you're sure to upgrade your CPU within the current year, going above 1.5 V doesn't seem to be a good idea. And 1.55 V is surely a no go for long term. After all, it only takes 36 hours to lose 5 mV off of your overclock.

 

Thank you so much... that is exactly the sort of info i was looking for, fantastic post!!!

If i knew my vcore max unstable/vcore min stable of my 4790K i'd test this myself but i don't, i can only guess that some degradation has happened by now.

You're the first person to ever convince me to lower voltages, now I'm at 1.37v for 5Ghz on my 8700K... my CPU sends it's thanks

 

^^ crazy good post! I wish the +rep system was working!

A frequently overlooked contributor to CPU degradation (or a shift in the Hz/mV response curve) is Load line Transients. Under voltage "clamped" conditions (eg, fixed vcore or vcore at load with dynamic voltage and frequency) when the current (read "load") changes there is an unavoidable oscillation of the voltage in that circuit - called load line overshoot (and undershoot). These transient spikes occur on the microSecond scale and are referred to as V_ovs by Intel in processor spec sheets. They are not something you can detect with a DMM (or OS tool), but require specific equipment, and ideally an Intel socket-specific tool. Anyway, MB mfrs added LLC to "compensate" for the load-line overshoot, but all LLC really does is allow for (or not) sufficient vdroop to give some headroom for the V_ovs with regard to the bios specified vcore/vccin delivery. It does not change the magnitude of the overshoot, just lowers the peak spike (by the amount of vdroop). So, long story short, defeating vdroop completely with LLC (eg... "holding a constant vcore idle vs load as measured by CPUZ for example) actually allows for some serious uSec voltage excursions well above the bios setting(s), leading to what we call degradation (or accelerated "aging" of gates/transistors). a uSec is a long time from a transistor's point of view. So, Vdroop is a good thing.

Depending on the vdroop allowed in the above experiment, the actual peak voltage is likely much higher that the set vcore, eg,. 1.7V (by more than 200mV during load transitions).

 

^^ crazy good post! I wish the +rep system was working!

Depending on the vdroop allowed in the above experiment, the actual peak voltage is likely much higher that the set vcore, eg,. 1.7V (by more than 200mV during load transitions).

well I have a 3930K that I set the voltage in BIOS to 1.73 volts for a 4Ghz clock on the CPU. the CPU has been running this way for 6 years now. the top voltage that the CPU hits at load is 2.03 volts, now I have been told that this is to high, but my CPU is very stable so it works for me. now on the down side is that I have had to replace my memory every year as the memory keeps failing on me.

 

Had a Sempron 140 ages ago I was trying to get >5Ghz with and killed it with 1.85v.

Other than that, never killed a CPU from voltage. Ran my i5 6400 at 1.475v (set in BIOS) for a few benches and it still made it 2+ years before I retired it.

 

yeah - killed is different from degraded... guess it is the ultimate degradation.

 

very good info in this post, I have been wondering the same thing myself, I almost wanted to run my 8700K at 1.45-1.5V just to see how long it would last, I decided against it though. Maybe a year from now I will get crazy with this chip and really push it, but for now I'm happy with it. I'm running 1.375v @5GHZ 23ish hours a day minning on this computer for several months now.

 

My first 4790k was ran at 4.9ghz w/ 1.37v and showed zero degradation signs after a year and a half of use. My current 4790k has degraded by ~200mhz in the 3 years I have had it. Was ran at 5ghz w/1.4v 24/7, with sub ambient temps on a TEC setup (avg load temps in the 40s). Now I run it at 4.7ghz since 4.8-5ghz is no longer stable on feasible voltages. I usually only keep CPUs for ~2yrs, so not a big deal for me. It's past due for an upgrade, I'm just waiting to decide on Ryzen2 or wait for the TR refresh. To be fair, it survived a pin rotted motherboard and has been through a lot of scares, so I'm just happy it still works :laughings.

Before those, I had a 3770k that lost roughly 150mhz in 2 years. That was one a turd though and only ran at 4.6ghz...any higher needed TONS of voltage.

Every CPU and setup will be different but depending on how hard you are running these chips, I would expect some slight degradation after a year or more. Don't be surprised if you have to drop your clocks 100mhz or so, or give another click more vcore to compensate.

All of my chips for the last 6-7 years have been on TECs though, so YMMV.

 

May be a relationship between HIGH VID and LOW VID chips (automatic voltages/SVID).
Something about "leaky" vs "non leaky" chips?
and lower VID chips running cooler, better overclocking on air, but responding worse to subzero, while high VID chips run hotter, have higher power consumption, but react better when kept cold?

 

lol - and for a frequency of 4GHZ? You should send that to Intel so they can study that anomaly.

Peace. Out.

 

yea I get that it is not the norm, but it's stable, and not fried, so I leave it the way it is. it does run hotter than the normal 3930K CPU with a 4Ghz clock on it. maybe when I am done with it I will, that is not a bad idea.

 

yeah, bottom line is current kills, not voltage. So, load and frequency play an important part.

 

This is one of the best threads i have read, thanks for sharing your data @audiotest

 

Thank you for your help. Even though all this is getting over my head a bit.

 

pretty amazing how quite it is - i was sure there would be lots o' tales to tell.

 

I am sure that there are plenty of great tales, but most people are just not into spotlighting there failures.
as a result we end up with short threads like this one, that could be filled with a great amount of useful information, but instead they are left baron with only a couple of peoples tales.

 

or, there not a lot of cpus dead just from vcore. On x299 and x99, VCCIN is more apt to fry a cpu... Cache and IMC kills are about as common as core kills.

 

Most people stop well before reaching the danger zone out of naturally wanted to preserve their chip. Those that push them to the point of causing outright death are few and far between.

I have killed 3-4 CPUs in my time, but not a single one was from voltage...all physical damage (cracked dies, pin rot, condensation, etc )

 

1.55 volts and old nvidia card killed my CPU + MB

Hey, my name is Achill and I have overclocked my AMD Athlon x4 880k to 4.5GHz and I accidentally used 1.55V, it worked for several hours under load without any problem at all, so I decided to keep it like this.
2 weeks after I was using my computer normally like everyday when a friend gave me his old GTX470 to test, I swapped it out with my GTX 980 and tried to boot up and suddenly my system made strange noises and started booting again and again. I ripped out this junk video card (without electricity of course) and then I noticed over the motherboards hardware speaker, that my CPU was dead.
Still dont know if the overvoltage caused that or just the old video card that was kind of abused and maybe was already dead.

 

Really glad I stumbled on this thread.
Thank you so much for all the effort that went into those 7700K CPU's.

@toolmaker03 - I really think you should contact intel about your CPU as it's absolutely redonkulous that it still lives with that vCore.
Perhaps there's something that can be gleaned from that specific sample's manufacturing results that could create more robust CPU's - of course intel probably would prefer you buy a new CPU instead of getting more time out of the old one by overclocking.
Regardless, I'm sure someone in their R&D department would love to look further.

My current 8086K (delidded with conductonaut) is sitting at 5.3ghz @ 1.39v fixed - I have the most aggressive LLC checked so it idles between 1.376 and 1.392v according to HWInfo.
BIOS is setup to allow max power to be drawn when needed.
I use Realbench as my test (4GB of memory for 4 hours) of choice since it's probably the most accurate in terms of what a dedicated gaming PC might endure.
Under full load HWInfo reports max Current (IOUT) of 139A but was in the 120A range for most of the stress test - average idle (desktop) amps are 20-30A for browsing etc.
Max Power (input) of 169W but was mostly in the 150W range during stress test, average idle (desktop) watts are 30-40W for browsing etc
Max CPU Package temps of 76C but mostly 68-69C throughout the test, average idle (desktop) temps are 27-35C for browsing etc
Are these values the correct ones to be looking at?

I have never liked adaptive voltage, especially so with this AsRock board as the spikes are IMO unacceptable.

I feel that the CPU has the CPU can do 5.4Ghz at 1.42v and remain within safe operating temps, and whilst I know that an extra 100mhz isn't much, the purpose of delidding and buying a binned 8086K was to get the maximum performance available.
I don't keep a PC beyond 3 years since I predominantly use for gaming and 3 years seems to be about the point where I look at a new build.
I've always overclocked and never had anything die except for mechanical drives.

I feel that 1.41-1.43V (fixed) is probably going to be ok for use 12-18 hours per day (idle/browsing about 70% of that time) but thought I would ask for opinions since there's some expertise in this thread?
I would never go above 1.45v and this data indicates over 1.5v is absolutely going to accelerate degradation.
Is there a strong consensus on what would be the upper vCore limit if the criteria were for the CPU to last 3 years without issue?

Thanks again.

PS - what is a "TEC" system?

 

PS - what is a "TEC" system?

well this is my extreme "TEC" water chiller.(thermal electric cooler)
https://www.overclock.net/forum/62-peltiers-tec/1651377-full-system-tec-cooling.html

 

...excellent question and subsequent info in this thread ! :thumb:

I have yet to actually kill a CPU outright, either via the fast OV max method, or the slow-boil at OV++ for years approach - but blind luck is a good thing Two additional, related issues to consider :2cents:

- Software voltage and current tools are better than nothing, especially when consistently used across different speeds, but there can be quite a divergence between different tools for the same task measurement. For hard-core (especially for sub-ambient / serious longer-term over-current), best to use EPS clamps and volt / amp meter. I have some HEDT CPUs which read anywhere from 1.32v max to 1.37v max for the same high-stress/loads runs...

- Temps play a big part in degradation also. I don't mind going to the high 1.38s if the highest specific core temp of a multi-core CPU stays under 80c, even with TJmax @105C. I have yet to measure any degradation (i.e. same CPU speed needs more vCore for same tasks at same temps) for CPUs which are 24/7 at 1.35v+ for several years if they they stayed well below 80 C max.

 

16.250v and my 9900K is fine

:ninja:

 

...ahem, just so you know, we're talking CPUs, not barbecues

 

I started with my 2600k back in the days at 4,8GHz but can't remember the voltage for the life of me but it was below 1,4V and IntelBurnTest was hitting low 90s °C, load was 40-50°C. After a couple of years I started having BSODs - I bumped up the voltage and all was ok. Another year or two have passed and I had to tune down the multiplier to 4,2GHz (goal was to finally have reasonable temps) until again after two more years I had to turn up the voltage a little bit. When trying to juice the little guy again to mitigate the frametime issues I started having in modern games I tried to see if I can touch 5GHz for fun. Nope, all I could get was 4,5GHz at 1,31V. Anything higher failed instantly regardless of hyper-threading being on or off. Then I told myself it's time to give the 8-year old veteran a new home and go for a refresh.

I wish I could give more detail than this, I'd just like to confirm that from my experience the degradation was real.

 

On the face of it, you should have gone to intel and reported the need for more voltage after only a couple of years (within warranty), but they would likely have said that as long as it could hold stock at 1.35v then they wouldn't do a thing.

But lasting 8 years and still only needing 1.31v I think is fine - that's just called 'getting old' in the useful life of a CPU.

5Ghz was likely never possible unless you wanted to go much higher on the voltage or delid.

I've never ran a PC build longer than 3 years, but I have all the old school components, even an original Pentium 4.
I might set up a rig and see how much the P4 will take before it dies!
Although it's (at least for me) a CPU landmark, so I might keep it for memories instead of frying it.

Thanks for your report.

 

What's the consensus on delidding with liquid metal with regard to degradation?
Does it make any difference because the heat is much lower?

Or is it all about current just the same as stock?

 

What's the consensus on delidding with liquid metal with regard to degradation?
Does it make any difference because the heat is much lower?

Or is it all about current just the same as stock?

this is only my opinion. as I do not clock my hardware to it's max and leave it their. I will build a system and about every 3 years clock the system a little further, in a effort to keep up with newer hardware. by the time I get to the third time I am overclocking the system I do not expect the system to last more than two years, because by this point I will have the system clocked to it's max stable clock speed. the longest I have had a system last at a max clock was my AMD939 FX60 this CPU lasted at a 3Ghz clock speed for 4 years before it died. most do not last more than a year. so to me the higher the clock speed, the faster the degradation will be. temps will help to slow this process down, but if you allowing your CPU to run at temps above 60C. you will see the system dying, faster than stock systems that run below 60C.

 

took 5 years of running my 3930k @ like 1.45 to see any change. in stability.

 

This is exactly in line with what I was thinking.

I doubt much will change in the 3-5 year life of a PC build if vCore is below 1.45v and temps are good.
There's virtually no data out there with numerous alarming stories about CPU deaths with vCore below 1.45 and good temp control, I think because it's very rare for a CPU to die or degrade to a point where it's a big issue.

 

I had a I7 6800k that died in a few months

 

That's a short life, but you forgot to mention how it 'lived' it's short life and what factors may have caused it's early demise?

Unless you were doing something crazy like 1.55-1.6vCore, ignoring insane temps etc. the only plausible reason would be that it was a lemon from the day it left the factory.

 

Very nice!! And thank you for sharing!
I have never been able to get good bench scores on Cinebench, (i7 8086K delidded @ 5.2Ghz all cores at 1.36vCore no AVX offset, 32GB DDR 3200Mhz, M.2 NVME, RTX 3080 etc), so there must be something 'special' people do when they run a bench?
Brand new Win 10 install with nothing else on it? Safe mode, or disable as much background stuff in Win 10 as they can before running?
Whatever it is, it's some secret benchmarking sauce I do not know about as my scores are never that good.

 

I have just closed all my apps and pulled out the displaycable of my second monitor. Daaamn you got a 3080 ?!?!?

 

1348 Single Core
10600 Multi Core

I probably need to do a fresh install of Win 10 as this one has been updated a few times with major updates, but low Cinebench scores are the norm in my experience.