Underclock! - How low can I go?

[Whitedog]

I want to build a PC to put in the corner of my den that only serves one purpose.
File sharing and file backup.

It will only have a basic video card in it ( I have an old G100) as I don't need anything but to display desktop crap.

I am wondering if I stuck a modern CPU/mobo and ran it as slow as possible if it would be less power consumption than if I used an older CPU/mobo?

Does anyone know any info on total system power consumption, or any place that has done any kind of comparison?

I'm not really trying to "save electricity", I am trying to reduce the heat output. My den is hot enough with the gear I have running in it, and I'd like to keep it as low as possible.

In the summer time, it is rediculously hot in here. I can be 72 in the hallway and 80 in the den. <shrug>

Anyway, I would be neat to be able to build a system that put out VERY LITTLE heat.
I only want 1 VERY SLOW running fan on the CPU, and 1 very slow running fan on the PS.

Cheers!

 

[Lonyo]

I had a Barton 2500+ downclocked to ~1.1GHz @ 1.1v
Used about 85w idle (according to a kill-a-watt thing) with 1GB RAM, 9800, 2 HDD's, 2 opticals (I think), 4 or so fans (case + heatsink fans).

When I go home tomorrow, I'm going to swap in a G200, 256MB RAM instead of 1GB.

 

[tallman45]

AMD had an APP called Cool an Quiet, lowers voltage and such to get a CPU down to 1ghz. Intel has a similar utility

 

[pm]

I spent a while messing around with system configurations while measuring the total system power using a watt meter (like this one: http://www.amazon.com/P3-P4400-Electric-Power-Monitor/dp/B000JLOKXI )

I started by using my previous computer - a Prescott Pentium 4 3.6GHz w/ 1GB RAM and a GeForce MX card. It's running CentOS 4.4 (Community Enterprise OS). I started at 122W idle. Downclocked the CPU, lowered the voltage and got to like 105W idle. Then I stripped out the video card and set up the computer with VNC and SSH for remote log in. This reduced it to 91W. Then I swapped in a smaller, more efficient power supply and changed some of the fans and got to 86W. Then I removed memory from 1GB to 512MB and got to 85W.

But, I still didn't like 85W. I finally gave up and bought a Via Epia M10000 ( http://www.mini-itx.com/reviews/nehemiah/ ) on Ebay for $50 (shipped). It's running 17W idle.

Old System:
85W * 24hours/day * 365days/year = 744kWh/year
744kWh/year * $0.08/kWh = $59 per year.

New
17W * 24hours/day * 365days/year = 148kWh/year * $0.08 = $12 per year.

I have it running CentOS 4.4 (which is supposedly super stable - 3 week uptime since I set it up) and it's running Samba (Windows file sharing), Apache (website), FTPd, and - probably most importantly for me, Asterisk for my home VOIP solution.

I've been using "rsync" via SSH for backing up and it's amazingly fast. I'm very impressed. It's like 10 seconds to run on about 22000 files (mostly digital photos) and about 12GB of data if nothing has changed. If things have changed, it updates over the network very quickly. The VOIP quality is great as well and the system has no problem handling a rsync while also carrying a phone call. So far I'm very pleased.

 

[Brunnis]

A cheap and very low power alternative is a 128kB L2 Sempron system. Get a mobo with some chipset other than Nvidia and try to get one with pretty much everything integrated (graphics too). Make sure that you get a Sempron with Cool 'n Quiet (3200+ and upwards on Socket AM2), otherwise you won't be able to downclock using lower multipliers. The positive thing about the AM2 socket is that you won't be limited to 1.1V as the lowest Vcore, like rev E was. AM2 CPUs will go all the way down to 0.8V. This, along with a 1GHz CPU clock, should make the CPU consume maybe around 2W during idle and around 4-6W under load. You should not need a CPU fan for that.

So, to answer your question: Yes, it is definitely better to build a system with modern low spec components than using old stuff. The nice thing with that Sempron is that, while it is cheap to buy, it will still provide relatively good performance even at 1GHz. Below is an article you might find interesting (I'm linking to page 5):

http://www.silentpcreview.com/article313-page5.html

 

[QuantumPion]

If a computer is on 24/7/365, and your average electricity cost is $0.10/kwh, then you will save $0.0072 per watt per month. In order to break even on the cost of a $30 kill-a-watt meter, you would need to save 417 watt-months or nearly 1100 megajoules!

 

[Whitedog]

Fantastic Replies! Great ideas.

Lonyo Looking Forward to your results!

PM Thanks, and that is a very interesting looking mobo.

CPU's I have laying around is an old XP1700+ (don't know the core) and an TBred (b-core) XP2100+

If I have to buy a mobo/cpu combo, no big deal though...

Again, I have everything else... including old video cards of various flavors.

The only thing in it that will be "modern" is hard drives.

 

[pm]

Originally posted by: QuantumPion
If a computer is on 24/7/365, and your average electricity cost is $0.10/kwh, then you will save $0.0072 per watt per month. In order to break even on the cost of a $30 kill-a-watt meter, you would need to save 417 watt-months or nearly 1100 megajoules!

True - the cost of the watt meter eats up a lot of the savings. But I got the watt meter as a Christmas present. Now it spends it's days getting passed from co-worker to co-worker.

Although your point about the cost of a watt meter vs. savings is a good one, I don't understand why you've converted to watt-months or megajoules - it makes the numbers appear larger, but most people pay their bills in kWh, so it seems more confusing to me to convert the numbers to megajoules.

Good luck, whitedog