Question What happens if you undervolt CPU too far?

[rbogomolec]

I've undervolted my RX 6800 XT GPU a bit too far so I started getting artifacts and also the game crashed once. I know that's normal and I'm still looking for the sweet spot. But what happens if you undervolt your CPU too hard? I have a i5 9400f (it doesn't bottleneck my GPU, at least not on 4k high settings 60fps lock, I did a bunch of tests and this CPU is doing a great job for my gaming demands). I did undervolt it quite hard though. I went as far as - 125mV and after running ThrottleStop's stress test for 45min everything was still fine and stable.

Now, when playing Shadow of Tomb Raider under the above mentioned settings, my CPU only draws between 10W and 25W. Everything is stable and the temperatures are great, clocks are hitting their max potential as well, but that is quite some little power consumption. Though, this particular CPU is said to draw around 60W even under max load, so it may not be that strange after all. What I'd like to ask you guys is: How do I know if my CPU is getting too little juice? In the case of GPU I know it's artifacts and game crashes. In the case of CPU, is it just the BSOD or are there other indicators as well?

Also, I had a lot of people tell me that there's no need to undervolt, but in my case it gives me better temps for both the CPU and GPU, while still being able to utilise the clocks at the max MHz. So please, don't bother telling me not to undervolt, cuz I'm a huge fan of it. 😁

 

[MrN1ce9uy]

I would have guessed 25-35W, so 10-25W is a little surprising. However, the Core i3 has been known for having little power consumption. As far as I know, the non-K variants of Intel's CPUs do not allow for voltage modification.

Also, to answer your question, if you undervolt your CPU too far it will either a.) not boot at all. or b.) work somewhat with intermittent errors. This should not (that I'm aware) harm anything except your workflow. Simply correcting the voltage would bring your back to normal.

 

[uWebb429]

But what happens if you undervolt your CPU too hard?

If you go too far your computer will not be stable and it will crash. You will usually see errors reported in the TS Bench test or your computer will not be game stable or it might crash when lightly loaded.

https://imgur.com/wadHedv

View: https://imgur.com/wadHedv


Somewhat surprising to most people, too big of an undervolt can cause more problems at light load compared to full load. When lightly loaded, Intel CPUs already reduce the voltage so a big offset undervolt on top of that can cause a BSOD.

Did you undervolt both the core and the cache? As long as your computer is 100% stable and the CPU is still running at full speed then your undervolt is OK. Less heat and less power consumption are always a good thing. Some people do not realize the dramatic difference an undervolt can make. My 10850K can run Cinebench almost 20°C cooler after an undervolt compared to default voltage.

As far as I know, the non-K variants of Intel's CPUs do not allow for voltage modification.

That is not true. The non-K variants can be undervolted exactly the same as K series CPUs. Intel has blocked out some processors in their XTU utility. If XTU does not work or if there are no options available in the BIOS, use ThrottleStop instead.

On newer 13th Gen CPUs, Intel has dreamed up a new feature called Undervolt Protection. That needs to be disabled in the BIOS if you want to undervolt. ThrottleStop 9.6 can report if this is enabled or not.

https://imgur.com/bpinOAW

View: https://imgur.com/bpinOAW

 

[rbogomolec]

I would have guessed 25-35W, so 10-25W is a little surprising. However, the Core i3 has been known for having little power consumption. As far as I know, the non-K variants of Intel's CPUs do not allow for voltage modification.

Also, to answer your question, if you undervolt your CPU too far it will either a.) not boot at all. or b.) work somewhat with intermittent errors. This should not (that I'm aware) harm anything except your workflow. Simply correcting the voltage would bring your back to normal.

Yeah, I was also surprised to see 12-18W most of the time while playing a demanding game in 4k. That's why I wanted to double check. The clocks are good though, almost constantly at 3.9GHz, just like they used to be when I didn't undervolt at all. Like I said, I did get some instabilities while gaming, but all of them seemed to be a classic case of GPU undervolting, not CPU.

 

[hotaru.hino]

One thing to point out with undervolting causing issues at light load but not a heavy load. Voltage is needed to drive the clock speed up. Under a light load, that's when boost clocks are at their highest, but if you limited the voltages too far, there won't be enough voltage to keep a stable clock. However, under heavy load, the clock speeds dial down a bit and it doesn't need as much voltage.

 

[rbogomolec]

If you go too far your computer will not be stable and it will crash. You will usually see errors reported in the TS Bench test or your computer will not be game stable or it might crash when lightly loaded.

https://imgur.com/wadHedv

View: https://imgur.com/wadHedv


Somewhat surprising to most people, too big of an undervolt can cause more problems at light load compared to full load. When lightly loaded, Intel CPUs already reduce the voltage so a big offset undervolt on top of that can cause a BSOD.

Did you undervolt both the core and the cache? As long as your computer is 100% stable and the CPU is still running at full speed then your undervolt is OK. Less heat and less power consumption are always a good thing. Some people do not realize the dramatic difference an undervolt can make. My 10850K can run Cinebench almost 20°C cooler after an undervolt compared to default voltage.


That is not true. The non-K variants can be undervolted exactly the same as K series CPUs. Intel has blocked out some processors in their XTU utility. If XTU does not work or if there are no options available in the BIOS, use ThrottleStop instead.

On newer 13th Gen CPUs, Intel has dreamed up a new feature called Undervolt Protection. That needs to be disabled in the BIOS if you want to undervolt. ThrottleStop 9.6 can report if this is enabled or not.

https://imgur.com/bpinOAW

View: https://imgur.com/bpinOAW

Yup, I did both core and cache. As for light load, I'm using this PC as a console most of the time, so it's either turned off or under heavy gaming load. Though, even when I'm doing light work on it, I never got BSOD so far. Really seems stable. It's just the super low wattage that surprised me. But in the end, it seems to be a good thing and nothing to worry about. The problem is that I'm also looking for the GPU undervolt sweet spot, so I want to make sure that my game crashes are really GPU dependent, not CPU. But since I've seen only my game crash and not the whole Windows Explorer, and no BSOD either, this would indicate that the game crash was GPU related, right? Also, next time I raised the GPU voltage by 20mV and the game didn't crash, but only gave me some artifacts on the in-game graphics. So I really think I went overboard with the GPU undervolting. Your reply also seems to indicate that. Thanks for the reassurance! 😁

As for the undervolt protection - I didn't know that. And I'm disgusted. Wtf, let people do what they want if they know what they're doing. Especially with undervolting, where you can't damage anything. Unless you save the lower voltages before making sure that everything is stable, but then it's the person's own fault.

 

[rbogomolec]

One thing to point out with undervolting causing issues at light load but not a heavy load. Voltage is needed to drive the clock speed up. Under a light load, that's when boost clocks are at their highest, but if you limited the voltages too far, there won't be enough voltage to keep a stable clock. However, under heavy load, the clock speeds dial down a bit and it doesn't need as much voltage.

Oh, I see. Never thought that undervolting could be an issue at light load as well... But in my case, the CPU has been stable under both light and heavy load so far. It's just that I'm amazed that it's drawing so little power. Same as my GPU. I've got an RX 6800 XT. In all reviews I've seen it draws around 300-400W. So I've bought a 850W PSU. But the biggest numbers I've seen so far were around 25W for the CPU and 130-140W GPU. 😂 And Shadow of Tomb Raider in 4k on high settings is quite a demanding game. I think it might be cuz I've locked my GPU at 60fps in the Adrenalin panel, so it saves a lot of unnecessary stress for those extra fps that I don't really want to have.