Undervolting your CPU

I recently bought a second hand Dell optiplex 9020 with an i7-4790 chip for cheap. It's a cute little SFF PC.

It gets to 80°c under full load which is a little high. I have spare thermal paste that I've yet to apply. Thought I'd try undervolting it first.

Has anyone else undervolted this particular chip? What kind of undervolt can I reasonably expect? I'd like to speed up the process a bit because my previous undervolting endeavors usually took about 2 hours of reducing the voltage and running Prime95 benchmarks.

I haven't undervolted a desktop PC before, but I've previously undervolted an i7-4700MQ & i5-6200u in laptops which both had a maximum stable undervolt of -0.095v. Improved the temps by ~10°c in both cases.

Feel free to post your own results. I'd be interested to hear them.

It's no use, put power saver profile with cpuz/hwinfo/monitoring software and check how low it will go, I'm 100% sure at power saving cpu will automatically downclock and undervolt itself.

I don't want to downclock or lose any performance. Undervolting my laptops maintained the clockspeeds and reduced thermal throttling under CPU+GPU loads, so I actually had a performance boost. I intend to do the same on my desktop. The core voltage offset is easily changed through software with Intel XTU. I just want to know a safe starting voltage, as I'm a bit too impatient to start from 0 for a third time.

Bump

80C is honestly fine, but I'm running at 1.067V

Haswell has automatic power states, probably it is the mobo that does not support it. I have a Intel Xeon 1231v3 on a cheap h81m gigabyte mobo and I never lose performance in games or in general with the auto power states.

I tried undervolting an i7 5500U (Asus F555L), but those ones are designed to use very little energy already.

It didn´t do anything for temps in the end. Just BSODS because it reached a point where the CPU was just starved, and made the system unstable.

Repasting reduced temps from 100-105 Cº to around 80 Cº

It got a dedicated GPU that was lowered from 96 Cº to 76 Cº as well.

So if its second hand, clean that shit well, try to lubricate the fans, and repaste.

Constant voltage? I'm only talking about applying a negative voltage offset, so it still steps down to like 0.5-0.6 volts at idle.
I don't lose performance for any other reason than thermal throttling on my laptops. The GPU and CPU share the same heat pipes and fan so things get a little toasty when using both. A gaming laptop with dual fans would probably resolve this, but I'm not a gamer, nor am I rich.

No, I just don't remember what the offset is. It's something close to a full tenth.

My i5-6200u (Also a low power chip) undervolted to a -95mv offset and is rock solid stable. The goal is not to push the voltage too far down so that it remains stable. I use prime95 to check for CPU stability. In the end I received a 10°c temp reduction and the fan is a lot quieter under full load too. It usually sits at 65°c under prime95 now. The laptop is still too new to justify repasting it just yet, but I have repasted the i7-4700MQ laptop, which dropped the temps by about 15°c.

Just go to windows power settings and cap it to 80% you dumb fuck

Then I'd lose performance. Why would I want that when there are viable solutions that don't affect performance at all?

Repaste regardless of if you succeed in undervolting. I think it's a tedious process though. I consider 20min in OCCT stable, because I'm no autist, but still you can clean out the dust and repaste it in 10mins.

Also I was wondering how do the laptops cope with undervolting when switching between battery and charger? I don't really care about thermals, already applied LM, but i'm considering it for the battery life.

80 degrees is OK.

If you want better thermals, you should just delid it.

I ran prime95 for about 20 mins before concluding my undervolts were stable. I scale back the undervolt by 15mv (0.015 volts) after reaching an unstable voltage. I've found scaling it back any less leaves the CPU in a state where it may still crash once every few weeks.

Switching from charger to battery, and battery to charger is a non-issue even under full CPU load. Just as long as you're at a stable undervolt (follow the advice I mentioned above).

I'll consider whether or not to repaste after I undervolt this chip.

80°c under a normal 8 thread 100% util. load.
Prime95 seems to push it up to 92°c though.

I think the fan curve on this Dell is set to use the minimum fan speed possible. It's very reluctant to spin the fan up. It waits until the chip gets really hot before it ramps it up from idle speed. I don't think I can do anything about that either.

This is the first time I've owned a desktop in 8 years. I bought a pre-built Dell because I'm still a n00b. The last thing I want to do right now is something that could possibly break my PC.

>I recently bought a second hand Dell optiplex 9020

Oh honey, why?

Cheap. A fair bit cheaper than building something of a similar spec new. It's also small, which is awesome. Can't complain at all.

I just found out about XTU today. IGPU overclocking is fun, adding 150MHz gives another 5-10fps on the only game i play.

ANY decently binned chip whether desktop or mobile should be able to do ~-125mV as an offset.

Set in XTU and let it run for a week to ensure stability. If you're looking for extra savings, do the same to the IGP. Most people don't realize that the IGP's use about the same amount of power as the actual CPU does.

Put some liquid metal on the die or on the IHS

Both of my laptops crashed at -110mv.
I haven't really bothered with the iGPU because I don't really know how to properly stress test it. Besides Open Hardware Monitor reports it using less than 1 watt of power most of the time I'm using the PC so I dunno if it's really worth it.

Laptop or desktop? I have a i3 6157U laptop with Iris 550, it won't let me fiddle with anything aside from voltages and current.

Does IGP still eat battery even with dedicated GPU?

It's part of the die, it's always under current. It eats jackshit if it's idle though. I'm not sure about linux, but in winblows it runs the desktop and everything for power saving, as it's still more efficient than dedicated cards, regardless of how low they are.

Laptop with an i5-5200u.

Laptops will use the iGPU for most applications even when the laptop also has a dedicated GPU. The iGPU is generally more power efficient so it makes sense that it uses it.

AMDs drivers automatically run games and high perf. 3D apps on the dedicated graphics, while Nvidias drivers often require you to manually select the dedicated graphics when launching an app.

>bought a phenom ii x6 1090t
>undervolted stock 3.2GHz to 1.225V
>idles at 0.7V
>cool as cucumber
:^)

Looks like I've been duped

I'm in the process of undervolting my i7-4790
Currently still stable at -90mv and running the prime95 stress test at 0.8 volts.
Seeing power consumption drop from 74 watts at stock, to 61 watts at -90mv. Temps and fan speed are lower too.
Wonder how much lower it'll go before dying.

Why not use throttlestop you it will apply every time you boot?

Just get a better cooling system. I run an i7 4790k at 4ghz all day and it doesn't come anywhere close to 80° C. The stock cooling that came with it certainly did though.