Effective undervolting/underclocking - how?

[poisonborz]

Hola,
I have a server (E5200 + GA-G41M-ES2L + 2 HDDs) – naturally in this case, speed is much less important than power consumption. So I thought it would be a good idea to toy around voltages: I whipped out my cheap power consumption meter, and entered the BIOS.

I found very little usable info on how to effectively do this, so what I did was simply lower the multiplier to the minimum and lower the vCore step by step. I've gone down to 0.85 (from the default 1.2), but – while the system was stabile, I found no traces of lower consumption.

Before the system idled at around 48W, after the setting it was like 45-46W. As I have a cheap measuring device (with a fault rate of prop. 3-4W), this could be next to nothing.

Is there something I did wrong? What is the lowest Watt rate one can get via such settings?
Thanks

 

[Magic Carpet]

Undervolting does minimum to your idle power draw. Consider getting a more efficient power supply unit and / or hard drives.

However, the cost involved in changing your equipment WILL offset possible gains in lower e-bills.

 

[ther00kie16]

Yea, idle won't matter much. Depending on your server needs, some routers may suffice. That would solve all your power draw problems.
A newer platform would also draw much less power. Been looking at laptops and Dell's Inspiron 14z and Vostro v131 with regular voltage mobile i5 draw around 8w idle with the display on. A nettop with a power brick would probably be in that range as well. Then, you'd be saving close to 300KWhr in a year, meaning it wouldn't pay itself off for at least 3 years.

 

[LoneNinja]

With modern power saving features most system have very similar Idle power consumption as is, undervolting will primarily save power under system load.

 

[Magic Carpet]

Really, take your average monthly electricity bill and work out whether it is worth the effort. Factor in different aspects like your own time messing with new hardware / software tuning. For some people, time is their biggest asset.

 

[Hugo Drax]

I got my asus GENE-Z set to offset - and then the voltage for offsetting at .16v

This keeps my 2600K idle temp at 27-28c
all 8 threads 100% doing workload 53c and vcore hits 1.096v at that level

 

[ther00kie16]

I got my asus GENE-Z set to offset - and then the voltage for offsetting at .16v

This keeps my 2600K idle temp at 27-28c
all 8 threads 100% doing workload 53c and vcore hits 1.096v at that level

Question isn't temperature but rather power. You wouldn't want to keep a 2600k loaded 24/7. On the other hand, a 20W nettop or 10W router would hardly matter. Also, the hardware in question is an older processor that probably doesn't power gate as effectively.

 

[poisonborz]

Thanks for all the replies.
By disconnecting the two case fans (as they were pretty useless in this setup) and some optimizing now I get around ~40W idle - I don't think I could go down more without sacrificing too much. It's actually pretty good for this system, probably thanks to the energy saving features of the Gigabyte board.

I choose this setup over a nettop because:
- cheaper to get (used laptops/netbooks even near this performance range would cost way too much).
- easier maintenance (a server runs 24/7, once something goes wrong in a nettop you can practically throw that out). also, used netbooks in lower price ranges are not known for reliability.

For a future server setup I'd probably build a PC with a motherboard that supports Atom. That would combine the very low consumption of mobile platform and the flexibility of a PC setup. The only downside is the really weak performance.
(update: after some reading, beefier Atom setups can also draw 30-35W, so there is not that much advantage http://www.newegg.com/Product/Produc...scrollFullInfo)

A lot to consider when you build a setup like this...

 

[Magic Carpet]

Low power market is going thru massive changes at the moment. I'd wait a bit. Or just build on Intel core technology now.

Power gating only works on Nehalem or later as well as AMD FX but really makes sense on 4c+ systems.

AMD dual-cores/ee quads are also very good in this department, albeit a huge bit slower ;-p

Atom? No way. Not in its current form. Shame on Intel. Even AMD-E is a better buy, in my opinion.

 

[know of fence]

With modern power saving features most system have very similar Idle power consumption as is, under volting will primarily save power under system load.

You do reduce both, and obviously load power consumption difference will be more pronounced. But measuring I had a similar experience. On Idle an Athlon II X2 went from 0,26 A to 0,25 A, kind of jumping back and forth. Under load, with SuperPi running the difference from under volting alone was around 15%.

Measuring AC power consumption gets kind of complicated. Those devices need a pretty high current (~0.02 A) to even start registering, so they fail measuring any kind of stand-by leakage reliably. And there is this whole thing about W vs. VA. You can precisely calculate VA by multiplying Amperage and Voltage (I've read some power companies do charge for VA), however this doesn't say anything about the real wattage that your PC consumes. Most of cheap electronic watt-meters can't properly measure wattage of anything but a light-bulb. Your best bet are either expensive electricity meters or those classic electro-mechanical counters, with the spinning aluminium wheel inside, they aren't all that precise (+-2% error) or user friendly but they properly measure wattage.