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CPU Low Power Draw CPU thread

Smanci

SFF Lingo Aficionado
Apr 21, 2017
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160
A bit off-topic but as we already have the Atom C2758 mentioned here, how is the performance of other slightly older low-TPD SOC solutions? ATOM330 even?

I'm looking into getting one for a U1 HTPC build (no 4k playback etc.) because of that nice power consumption and low price. J1800 for sure would be adequate but there's a great number of other options and I'm a bit lost...
 

zovc

King of Cable Management
Jan 5, 2017
852
603
The Atom C2758 did not give playable framerates in League of Legends with a GTX 1070 hooked up to it from my experience. Sometimes even YouTube bogged it down. I wouldn't recommend it for any sort of computer where a user would be directly controlling and operating system and programs on it.
 
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zovc

King of Cable Management
Jan 5, 2017
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If you want a low power CPU that's functional, look into getting a cheap modern CPU that you can undervolt. I'm pretty sure Intel lets you undervolt/underclock non-K CPUs, since I've been able to do that one every laptop I've tried. Just get the most affordable most modern CPU you can and turn it down you find your happy median of power consumption and performance. And stability, of course
 

msystems

King of Cable Management
Apr 28, 2017
804
1,405
This seems like a good place to discuss customized turbo boost settings in the case of being limited on power.

What I have experimented with is limiting the boost TDP quite heavily (in the 60 watt range, instead of 100+ watts) on a 6700K, yet still allowing the max multiplier to be set quite high, like 48X. What happens is interesting, single or dual core work loads still get boosted to 4800mhz ,since their power consumption is still below 60 watts. The unusual part is what happens under four cores. There isn't enough power available, so of course it does not boost to 4800 mhz, but actually, sometimes it doesn't even maintain the stock frequency, as in-- it will downclock to 3.8 GHZ when four cores are in use. I would really like to know why it does this, but I assume it has got to do with how the processor is estimating the VID needed. When it hits the power limit, it immediately downclocks, but is not very good at estimating the power demanded for the reduced clockspeed, it estimates very conservatively and there is no way to change it.

It sort of reminds me of what happens when a limit is reached in Nvidia Boost 3.0, except with that, the user can set the clock speed curve themselves, so it is much more efficient.

Also:
Asus has a BIOS setting allowing the maximum multiplier to be customized depending on the cores in use, however it doesn't work for me. If it did, then this could be tweaked perfectly so the power limit is never hit and the processor won't try to reduce the clock speed.
 
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Smanci

SFF Lingo Aficionado
Apr 21, 2017
126
160
I appreciate your educated opinions. However being the person I am, I noticed an n3150i board (+ shifty ThermalFake SFX PSU) going for 40€, briefly tried a W10 laptop with the same chip and decided it's enough. Seems like the thing has enough punch for 4k30 and the regular web browsing. I'l likely be running Linux anyway.

So this will likely be a sub-100€ impulse buy second-hand HTPC. Basically some functional special waste hidden in a classy aluminum shell.
 
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robbee

King of Cable Management
n3rdware
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Sep 24, 2016
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I appreciate your educated opinions. However being the person I am, I noticed an n3150i board (+ shifty ThermalFake SFX PSU) going for 40€, briefly tried a W10 laptop with the same chip and decided it's enough. Seems like the thing has enough punch for 4k30 and the regular web browsing. I'l likely be running Linux anyway.

So this will likely be a sub-100€ impulse buy second-hand HTPC. Basically some functional special waste hidden in a classy aluminum shell.

I've rocked that chip for a while too as HTPC and it's quite awesome. The price you're paying is really worth it. Only problem I had with it is that I couldn't get used to 4K desktop use at 30fps... For movies on the other hand, there's no problem.
 

CC Ricers

Shrink Ray Wielder
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Nov 1, 2015
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I have a i3 4130T that maybe, hopefully I can upgrade to a i5 or i7 of the same generation. My motherboard's chipset is Z97 so voltage options should be a non-issue. I'll probably buy a regular non-K CPU (they are usually cheaper than the T variants) and limit the turbo on that.

My goal, as making a casual mix of gaming and programming/production, to prioritize low power use on the CPU first, then use the extra headroom left for a GPU.
 

ej24

Minimal Tinkerer
Aug 28, 2017
3
10
I have a i3 4130T that maybe, hopefully I can upgrade to a i5 or i7 of the same generation. My motherboard's chipset is Z97 so voltage options should be a non-issue. I'll probably buy a regular non-K CPU (they are usually cheaper than the T variants) and limit the turbo on that.

My goal, as making a casual mix of gaming and programming/production, to prioritize low power use on the CPU first, then use the extra headroom left for a GPU.

I got the 4130t thinking it'd be decent and low power but I found it was regularly running at 100% just doing normal tasks. I jumped up to a Xeon e3-1275L v3 (aka i7-4790T) for $90 on ebay. It's my favorite cpu ever! It runs on any 87 or 97 series motherboard. I like it even better than my i7-4770T which is really close in performance but I've found the 4 core boost on the Xeon (again same as 4790t) is about 300-400mhz higher than the 4770T and single core boost is at 4ghz. It's nuts. Definitely consider a Xeon cpu on the 1150 platform. Any E3 12xx v3 cpu should work. The ones with an "L" in the name are low power.

Out of curiosity Ive tried downclocking and undervolting my 4790K to match the 4790T and it failed to boot so badly it somehow corrupted my bios... So I think there is definitely some binning involved in Intel identifying the best low tdp cpu's.
 
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Kmpkt

Innovation through Miniaturization
KMPKT
Feb 1, 2016
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I am in the process of shipping my processor set (7700T, 7700 and 7700K) to @zovc in the US to do the benchmarking for me. I work 50+ hours a week, have three small children and have three side businesses in addition to my day job at the moment. I frankly just don't have the time to do benchmarking. Additionally I discovered while doing the AsRock Deskmini piece that running benches is too under stimulating for me to be able to do on a repeat basis.
 

zovc

King of Cable Management
Jan 5, 2017
852
603
On that note: If there are any particular tests you folks are interested in seeing (or particular methods for measuring my tests, etc), please let me know!

Chances are, within a week or two of receiving the parts I'll have done all the testing I need and should have data and charts generated. (Any advice for rendering attractive charts?) From there, I'm going to try writing something up for the site and maybe also try out the "tech YouTuber" thing.
 
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Hifihedgehog

Editor-in-chief of SFFPC.review
May 3, 2016
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www.sffpc.review
I'm pretty excited for Coffee Lake i7-8700T, should be the first time we break the barrier of 3Ghz base clock on a 35W CPU :)
I'm hoping for a 3.0Ghz with 4Ghz turbo boost. It will be one hell of a chip! I can only imagine what 10nm is going to bring to the table!
Based on the latest round of leaks, the Core i7-8700T has a base of only 2.4 GHz and a maximum single core turbo of 4.0 GHz. Given that Coffee Lake mobile in 4C/8T already struggles to break 3.0 GHz for all cores with a 25W TDP Up configuration, it is reasonable to conclude that the 8700T is not likely going to be any better than its sibling. Seeing that there is only 10 extra watts TDP allocated for two more cores compared to Coffee Lake mobile, I predict all-core turbo will be around 2.5-2.6 GHz maximum.
 
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