Powerfull enough CPU with lowest IDLE power consumption?

kike_1974 · Post by **kike_1974** » Thu Mar 08, 2007 8:00 am

I'm looking for a CPU with low consumption at idle.

I'm using a C2D in my gaming PC because for this one I'm more interested in power consumption at load.

But I want to build another computer for my wife that is going to be at the same time a 24/7 file server. Most of the time it will stay at idle. But sometimes, maybe 1-2 hours/day it will be used for general use (office, some movie playing, some compressing/decompressing archives...). So I want something better than a simple sempron, I think I'm going the dual core route, but I need very low consumption at idle. Load power consumption is not so important for this computer.

I'm a heavy undervolter, so I will undervolt it as much as I can both for idle and load at the minimun possible and maximun possible frequencies (without FSB overclocking). I usually run crystalcpuid or rmclock to set two states for idle and load, undervolting as much as I can each of one.

So I'm looking for a dual core processors with the lowest consumption at idle when undervolted at is possible minimun. I've seen that the ones that could be more suitable to my needs would be 65nm brisbanes, 90nm EE windsords, the new 4xxx intels and mobile C2D.

My questions:
1) Can brisbanes be undervolted to 0,7V or lower at idle?
2) Can EE windsords be undervolted to 0,7V or lower at idle?
3) And 4xxx new intels?
4) And mobile C2D?
5) Which one do u think that will have lower consumption at undervolted idle?

Spare Tire · Post by **Spare Tire** » Thu Mar 08, 2007 8:09 am

From experience, Windsor undervolts down to 0.800V stable. The bottom is even lower but it just crashes below 0.800V. At that voltage, the CPU runs at room temperature, around 24C.

Delta_42 · Post by **Delta_42** » Thu Mar 08, 2007 9:10 am

CPU voltage is only one factor for power consumption...

Here is a review of the Asus N4L-VM board which shows a fully configured system with a Core Duo processor, Raptor hard drive and 2Gb of memory using the onboard graphics which should be ok for what you want. The whole system drew 68W at idle and 89W at full load.

I'm running a T7200 Core2Duo on the same board, at idle (including minimal use) it will clock down to 1Ghz and drop the voltage to 1V as standard. I don't have the equipment to measure power usage though.

kike_1974 · Post by **kike_1974** » Thu Mar 08, 2007 9:47 am

I owned a s939 processor (4600+) and software undervolting was locked at 1,1V, so it wasn't useful for what I needeed. That is why I think that the undervolting capabilities of a processor are very important, although I agree that they are not the only factor in power consumption.

And that is why I also ask which undervolted processor has the lowest power consumption at idle

jaganath · Post by **jaganath** » Thu Mar 08, 2007 10:51 am

I owned a s939 processor (4600+) and software undervolting was locked at 1,1V, so it wasn't useful for what I needeed

AM2 doesn't have the 1.1V Vcore lock.

that is why I also ask which undervolted processor has the lowest power consumption at idle

Hard to answer this one definitively without SPCR review-type testing. Core Duo, mobile C2D, Pentium M, AM2 X2 3600, all very likely <10W when undervolted to the max. Is budget a factor?

merlin · Post by **merlin** » Thu Mar 08, 2007 11:33 am

kike_1974 wrote:I owned a s939 processor (4600+) and software undervolting was locked at 1,1V, so it wasn't useful for what I needeed. That is why I think that the undervolting capabilities of a processor are very important, although I agree that they are not the only factor in power consumption.

And that is why I also ask which undervolted processor has the lowest power consumption at idle

I don't think the undervolting is limited so much by the processor as it is by the motherboard. Most motherboards have limits as to how low you can go, some of them don't even have undervolting options in the bios. Either way, if you're seriously focused on this, go for a laptop chip and undervolt that. I'd also be really careful choosing the motherboard and other component if power is such a major concern. (Although I think the difference in power consumption is only going to amount to $10-20 a year)

jojo4u · Post by **jojo4u** » Thu Mar 08, 2007 12:35 pm

So you have to split your question in CPU and platform. Undervolting is only the ice on the cake. About the undervolting of Athlons, look here (it's a bit behind because of lacking input, though)

CPU
Conroe: no
Netburst: no
Merom/Yonah: ok
AM2 Athlon: ok

All other CPUs are too slow.

1) Can brisbanes be undervolted to 0,7V or lower at idle? - 0,7 is bit extreme, 0,8 - 0,9 is possible
2) Can EE windsords be undervolted to 0,7V or lower at idle? - see 1)
3) And 4xxx new intels? - VID is locked @1.1+V, further BIOS undervolting possible on certain boards, but no idle/full load profiles, further hardware-modding possible
4) And mobile C2D? - VID locked @0.95V, see 3)

About platform:
AM2 with single-chip nforce or AMD 690 are reported under 30 W.
Only example to my knowledge of sub 30 W with Yonah/Intel is here.
Btw, what about a Mac?

checklist:
PicoPSU
2,5" hdd
1 RAM stick
no discrete VGA

links:
viewtopic.php?p=268055#268055
viewtopic.php?p=262839#262839
http://www.silentpcreview.com/article313-page1.html
viewtopic.php?p=272434#272434
viewtopic.php?p=300802

kike_1974 · Post by **kike_1974** » Fri Mar 09, 2007 5:22 am

Thanks for all your answers, I think I have more knowlegde now about this.

Budget is a relative problem. I mean, I would spend 30% more money if I get more benefits, lets say for example 15% lower power consumption. But I wouldn't spend 100% more money to get a 15% lower power consumption.

Taking your answers into account, I think I will go the brisbane route. C2D are vidlocked so I think not an option, they are also known to consume more at idle than athlons.
C2D mobile are vidlocked too, and though they consume less power, they are way more expensive.
So options are brisbanes and windsords, it is good to know that AM2 athlons are not vidlocked. I think brisbanes will consume a little lower because of the 65nm technology.

It would be nice to have a database with undervolting values of different processors. The post with database with athlons with 1.1V vidlock is Ok, but I think it would be more interesting a database with values.

Tonight I will add a post with values of undervolting of several processors I've owned in the last two years. I hope more people will add theirs

Thanks again for your help

frostedflakes · Post by **frostedflakes** » Fri Mar 09, 2007 10:17 am

I'd definitely recommend the X2 3600+. The system in my sig idles at 41w with CnQ enabled (default settings 1000MHz 1.1V), by the way. Undervolting the processor even further at idle has little effect, but you can go ahead and do it if you are so inclined. I personally didn't have much luck running the CPU at 800MHz 0.8V idle, though, I would get crashes. I think the lowest at idle it would go was 0.85V or so. But I was able to undervolt to 0.975V load at 1.9GHz. Dual Prime95 stable.

kike_1974 · Post by **kike_1974** » Fri Mar 09, 2007 2:17 pm

Yes, I think that is the one I will get. Would you recommend that asrock mobo? Can the fans be controlled with speedfan in that board? Does it have DVI output?

ronrem · Post by **ronrem** » Fri Mar 09, 2007 10:49 pm

The Brisbane 3600 would be fine. However-the tasks you describe would not posh an XP 1800,so a Sempron 3000 would probably give all you really would use.

wdekler · Post by **wdekler** » Sun Mar 11, 2007 1:45 am

The C2D 4300 also idles at 1.0gHz, so that's a good choice as well. And it can be overclocked to very good performance levels.

dragmor · Post by **dragmor** » Sun Mar 11, 2007 5:29 pm

wdekler wrote:The C2D 4300 also idles at 1.0gHz, so that's a good choice as well. And it can be overclocked to very good performance levels.

1.2ghz, it drops the multipler to 6x

ronrem · Post by **ronrem** » Sun Mar 11, 2007 7:55 pm

The Samsung T series full size HD's are very close to the notebook M series in terms of noise + wattage---but are much quicker and more GB per $

frostedflakes · Post by **frostedflakes** » Sun Mar 11, 2007 9:29 pm

kike_1974 wrote:Yes, I think that is the one I will get. Would you recommend that asrock mobo? Can the fans be controlled with speedfan in that board? Does it have DVI output?

I wouldn't recommend it or discourage buying it, I'm just kind of neutral on it. Hasn't given me any serious problems (other than out of the box it wouldn't work right w/Brisbane, had to update the BIOS -- stuff like that is to be expected, though), wasn't too expensive, and I've used ASRock for a few other builds w/out problems, so I guess on the whole I'm just comfortable with the name and what they offer for the price. I mainly got it though because of the single die chipset, which should offer lower power consumption than a dual chip solution.

I know for sure CPU fan can be controlled with Speedfan, I never tried any of the other fan headers, though. It does not have a DVI port.

kike_1974 · Post by **kike_1974** » Thu Mar 15, 2007 6:12 am

Well, I can't decide on the motherboard. I've read some information from the links that jojo4u provided about the power consumption of 5 different mobos (by the way, those links were very helpful for me, thx jojo4u). In this link, to be more concrete:
from here viewtopic.php?p=300802

I would like the board to have DVI, but it seems that the boards with DVI output consume 10-15W more. How is that a simple DVI output consume so much more?

Isn't there a motherboard with DVI output with low power consumption?

jojo4u · Post by **jojo4u** » Thu Mar 15, 2007 4:32 pm

kike_1974 wrote: Isn't there a motherboard with DVI output with low power consumption?

The 6150 needs quite a lot, but there are. You could try the new single-chip MCP61. Some are offered with DVI.
I am aware of the ASRock ALiveNF6G-DVI and ALiveNF4G-DVI and Asus M2N-VM DH.
Also the AMD 690G is quite good.

viewtopic.php?t=38736

http://techreport.com/reviews/2007q1/am ... ex.x?pg=16
http://www.hothardware.com/viewarticle. ... =935&cid=3
http://www.pcper.com/article.php?aid=37 ... ert&pid=12

EDIT: Geforce 6100 -> MCP61

david25 · Post by **david25** » Fri Mar 16, 2007 10:32 am

I have the same board with a 2.1Ghz Merom, 2Gb, 7600gt, HD, CD and it idles around 50 watts (using a cheap meter)

Delta_42 wrote:CPU voltage is only one factor for power consumption...

Here is a review of the Asus N4L-VM board which shows a fully configured system with a Core Duo processor, Raptor hard drive and 2Gb of memory using the onboard graphics which should be ok for what you want. The whole system drew 68W at idle and 89W at full load.

I'm running a T7200 Core2Duo on the same board, at idle (including minimal use) it will clock down to 1Ghz and drop the voltage to 1V as standard. I don't have the equipment to measure power usage though.

jojo4u · Post by **jojo4u** » Sun Mar 18, 2007 2:54 pm

david25- http://www.silentpcreview.com/forums/viewtopic.php?p=289256#289256 wrote:HI, I have the Asus MB with a T7200 merom and 7600gt, uses 70 watts at idle and around 100-ish on load.

david25 wrote:I have the same board with a 2.1Ghz Merom, 2Gb, 7600gt, HD, CD and it idles around 50 watts (using a cheap meter)

Looks like magic to me ... How come the drop from 70 W (which is reasonable) to 50 W (which would be a big suprise)?

dhanson865 · Post by **dhanson865** » Sun Mar 18, 2007 5:15 pm

FWIW the 90nm AM2 4200+ 65W TDP part just dropped a third of its price this week. They can be found for about $110 shipped in the US.

That is at 1.25V stock voltage so the TDP should drop nicely when undervolting.

The 90nm AM2 4600+ 65W TDP part dropped a similar amount, has the same stock voltage and can be had for about $140 shipped in the US.

Of course for many uses the 4600+ is overkill (as are any Core 2 Duos) but I thought I'd mention them just so you know there is a price shift occurring and looking carefully or waiting a few days could mean a large difference in the price you pay.

The Brisbane 65nm parts will have lower power draw at idle but there is a noticeable price/performance advantage for the 90nm parts until some point later this year (hopefully very soon) when the 65nm floodgates open wide and the 90nm parts can no long compete on price.

It's also highly significant that most of the 65nm Brisbanes I'm seeing are OEM/Tray parts with no HS/Fan and most of the 90 Windsors are retail parts with a stock HS/Fan included. To me that is worth $10 to $20. Depending on how many spare Heatsinks you have laying around that may not matter to you.

In price order the choices for AM2 socket dual core are:

$90 OEM Brisbane 1.9 3600+ 6x TDP
$110 Retail Windsor 2.2 4200+ 6x TDP

$140 Retail Brisbane 2.1 4000+ 6x TDP
$140 Retail Windsor 2.4 4600+ 6x TDP

I haven't seen any reasonable prices on lower TDP parts (for example I see $400 for a 35W 3800+ but I can't imagine anyone paying that price) and I've made sure not to include prices for any 80+ TDP parts.

simonnance · Post by **simonnance** » Mon Mar 19, 2007 5:29 pm

currently testing my C2D E6400 @ 0.95V

anything much under that, and it just wont boot!

http://extreme.outervision.com/PSUEngine
tells me that it makes my CPU draw a meagre 35W. Not sure how realistic that is though, any way of testing?

Poodle · Post by **Poodle** » Mon Mar 26, 2007 9:27 pm

Why not an new Amd 690 board? Quite many feats on that chipset.

Too bad Asrock don't make any though as their bios rocks on uATX boards.

jaganath · Post by **jaganath** » Tue Mar 27, 2007 2:11 am

tells me that it makes my CPU draw a meagre 35W. Not sure how realistic that is though, any way of testing?

you could get a device like a kill-a-watt meter to measure total consumption, and then work it out from there, or a multimeter to measure current through the PCB traces,but that would be more difficult I think.

gksam · Post by **gksam** » Tue Mar 27, 2007 10:09 pm

Poodle wrote:Why not an new Amd 690 board? Quite many feats on that chipset.

Too bad Asrock don't make any though as their bios rocks on uATX boards.

I recently built a computer using the Asus M2A-VM (AMD 690G), with 4200+ EE 65W 90nm, 2x1gb, 1x250gb (WD), dvdrom drive. With the kill-a-watt, it would draw around 57W for the whole system at idle (not including monitor of course) (cool n' quiet enabled).

kike_1974 · Post by **kike_1974** » Wed Mar 28, 2007 2:30 am

I still haven't decided the motherboard

This AMD 690G solution sounds good, especially because I think that the integrated graphic solution is a bit faster than the nvidia 6100/6150.

If that system draws 57W without undervolting beyond C&Q, maybe it could go under 50W when undervolting. I think it has DVI or HDMI, does it?

I'd like to see more experiments of power consumption in that asus board

Powerfull enough CPU with lowest IDLE power consumption?

Powerfull enough CPU with lowest IDLE power consumption?

voltage not the whole story

Re: voltage not the whole story