Why does my system use so much power?

wumpus · Post by **wumpus** » Sat May 26, 2007 12:35 am

I posted a blog entry about my upgrade to a 85% efficient power supply, based on before and after kill-a-watt measurements..

http://www.codinghorror.com/blog/archives/000871.html

After posting it, I noticed that my IDLE load on this particular system is 185 watts, which is ridiculously high! WTF?

System specs are in the blog post so I won't repeat them here.. but I can't for the life of me figure what is using all that power. The only thing overclocked in this system is the CPU.. I just checked CPU-Z and it's showing 1.360v for the 3.2 GHz Core 2 Duo which isn't THAT high.

Ideas welcome!

Atmosper · Post by **Atmosper** » Sat May 26, 2007 1:21 am

Your power draw is high because you have two videocards and an overclocked CPU. The 1900XTX is quite a power hog.

sjoukew · Post by **sjoukew** » Sat May 26, 2007 2:13 am

The ati 1900 xtx will consume a lot of power. I found some information on it on xbit.

Idle 28 watt, full load 120 watt.

I should check if EIST (Enhanced Intel Speed sTep) is enabled, that would lower the idle power consumption, but I thought that was disabled when you manually set the core voltage, therefore your idle power consumption is so high.
In windows, when EIST is enabled, in the controlpanel -> power options -> select "minimal power management" that setting will have the effect that when your computer is idling it will reduce the clock frequency and the core voltage, to save energy. But I don't know if this works with an overclocked cpu.

But you can see what the difference is to set your cpu to the default clock and voltage with eist enabled. Just give it a go

Post by **MikeC** » Sat May 26, 2007 6:34 am

The power consumption does seem very high, and the difference between idle and peak seems too small.

You already know about the ATI X1950XTX / Pentium D950 I profiled in Power Supply Fundamentals: 119W idle, 298w max (w/vidcard engaged). Note how much bigger the difference is between idle and max than your system's 185w/247w.

The main difference between that system and yours is the Radeon X1550 secondary video card and the Creative X-Fi sound card -- I just can't see those components adding 66W at idle. And if anything, the 10% oc'd D950 in my sample rig should draw more power than your oc'd C2D.

My guesses about your high idle...

-- power hungry processes running in the background that need to be turned off.
-- the price of those 2 vidcards in idle? Only way to check that is to replace them both with a single low power one and see what happens
-- does the OC mean EIST is off? That, in combination with the vidcards, might be enough to push the idle up that high.

wumpus · Post by **wumpus** » Sat May 26, 2007 10:31 am

Thanks for the responses.

EIST is definitely on; I can watch the voltage/clock speed/multiplier change in real time using CPU-Z.

I'll play with it a bit more, and try removing stuff. Right now I suspect the video cards. Maybe the X1550 is more of a power hog than I realized, or maybe I got a bum X1900XTX or something..

Post by **MikeC** » Sat May 26, 2007 10:52 am

wumpus wrote:Thanks for the responses.

EIST is definitely on; I can watch the voltage/clock speed/multiplier change in real time using CPU-Z.

I'll play with it a bit more, and try removing stuff. Right now I suspect the video cards. Maybe the X1550 is more of a power hog than I realized, or maybe I got a bum X1900XTX or something..

AFAIK, the X1550 is simply the X1300 w/ higher clock and renamed after AMD aquisition; the X1300 power demand was only ~30W max...

Lawrence Lee · Post by **Lawrence Lee** » Sat May 26, 2007 2:09 pm

Try using RMClock or CrystalCPUID to manually undervolt/underclock lower than EIST. Also underclocking your X1900 should knock off a few watts as well.

Out of curiosity what motherboard are you using?

wumpus · Post by **wumpus** » Sat May 26, 2007 3:23 pm

I'm in the process of upgrading my video card, so I pulled the X1550 to see what happens.

At desktop idle, with X1550 + X1900 XTX:
185 w

At desktop idle, with X1900XTX only:
165 w

So the X1550 uses 20 w at idle, I think.

This card was only used for 2D work anyway (to support my third monitor), so it was never under 3D load.

wumpus · Post by **wumpus** » Sat May 26, 2007 3:36 pm

I swapped out the X1900XTX for the X1550, and got the following:

X1900XTX at desktop, idle:
165 w

X1550 at desktop, idle:
149 w

so if X1550 draws 20w, that means the baseline power usage of this system, without ANY video card, is 129w. That still seems extraordinarily high..

Oh, and I forgot to answer on the motherboard question; I'm using the Asus P5B deluxe. Here's a screenshot of CPU-Z of my system at idle. EIST is definitely working..

wumpus · Post by **wumpus** » Sat May 26, 2007 3:54 pm

X1900XTX at desktop, idle:
165 w

X1550 at desktop, idle:
149 w

NVIDIA 8000 GTX at desktop, idle:
225 w (!)

(I know, I know, I am a game junkie and I got an incredible deal on a new GTX from a hardware editor I know.)

Still, it's a mystery to me why my baseline power usage on this system is a whopping 129 watts with no video card installed:

- Core 2 Duo 3.2 GHz CPU (overclocked, overvolted)
- Western Digital Raptor 150 GB primary hard drive
- Seagate 750 GB secondary hard drive
- Creative X-Fi sound card

I can try unplugging some more stuff, but I really think it's unlikely that the sound card or the two hard drives are using more than 20w between them all. That leaves me at 109 watts power usage for the motherboard + CPU, which is pure craziness.

Post by **MikeC** » Sat May 26, 2007 3:58 pm

The Asus P5B Deluxe is known to draw higher power than most motherboards. This reviewshows 3~4W higher power draw than an Asus P5W-DH and 8W higher than an Intel 975 board.

But 129W for the baseline power usage of this system without video card is very high, higher than any of the systems profiles profiled in Power Supply Fundamentals. The very worst of those is an Intel Pentium 670 (3.8GHz Prescott w/o EIST) + nVidia 6800GT card system at 141W idle.

The HDDs don't pull >20W at idle, for sure.

Try pulling the sound card, then reset the CPU back to normal clock speed: Nothing else left to try if you've eliminated mystery windows processes.

wumpus · Post by **wumpus** » Sat May 26, 2007 5:41 pm

I set my E6600 to stock speeds and now I get 197 w at windows desktop idle (down from 225 w, as I'm planning to stick with the 8800 gtx).

So the CPU overclocking accounts for 28w of the total.

I also know the secondary 750 GB hard drive accounts for 10w of the total as I can see the kill-a-watt drop by exactly 10w when that drive goes to sleep (I can hear it go to sleep, so I know when to look).

Assuming the raptor uses maybe 15w, and the sound card 5w.. that leaves us with:

129 - 28 - 10 - 15 - 5 = 71 watts at idle for a stock E6600 on the Asus P5B Deluxe motherboard with 2GB of DDR-667 and no video card. Sound right?

It looks in the ballpark based on these TechReport numbers:
http://techreport.com/reviews/2007q1/at ... ex.x?pg=12

Athlon FX-60 system, idle: 129 w
Core 2 Duo E6700 system, idle: 120 w
my system, idle: 145w (with X1550 video, overclocked CPU)

My system also has a second hard drive and X-Fi sound card. Full system config for the tech-report rig is here:
http://techreport.com/reviews/2007q1/at ... dex.x?pg=2