Proving you don't need a huge PSU to run a Hi-End System

[hardnrg]

With one 2900XT apparently using 240W, I'd probably go with a 1kW psu for a fully loaded, overclocked, and overvolted 2900XT CF system...

[ccokeman]

My thought fall along the line of why push it to work at 100% load just to keep up. Does it not become more inefficient as the load and power supply temperature increases.

[jammin]

It's a possibility that CF 2900XT's might need some of the more powerful PSUs out there.

I'll be interested to see what the minimum they will run on.

Considering that you can run a pretty loaded PC with SLi GTX on less than 600W, then I still don't see 1000W being needed.

Of course if you start seriously overvolting it's hard to say.

[jammin]

My thought fall along the line of why push it to work at 100% load just to keep up. Does it not become more inefficient as the load and power supply temperature increases.

 

Most PSUs reach maximum efficiency towards the top third of their rated wattage.

High powered PSUs are often much more efficient at high loads then they are at low loads.

 

Also, decent PSUs are rated to run their rated wattage for long periods of time, and you are unlikely to be running at maximum load 24/7.

It is nice to have a little overhead, but if that overhead gets into several hundred watts, then it starts to seem a bit stupid to me.

[romeo55]

I think this is a great idea

 

The reason why many are under the impression they need some crazy high end power supply is because when buying parts, rarely will you be able to calculate how much power you really need, which is unfortunate

 

Yeah, I've been wondering about this for awhile. In general, power usage has actually gone down, not counting the HD 2900s which is pretty much the only cards that doesn't fit this bill.

Edited May 21, 2007 by The Unforgivin

[road-runner]

Well its probably a good thing I got a 1000 watt if that 2900 draws 240 watts in case I do go crossfire with it that would be 480 watt on the video cards alone not OCed

[ccokeman]

480 watts at 12v is different than 480 watts at 110v but i don't remember the conversion to amps to run that out.

[jammin]

AMD quotes a peak power of 215W as far as I know

 

With overclocking this can go up of course, hence the 8-pin connector (2x6pin is limited to 225W I think?)

 

If someone finds reliable looking tests figures for actual card power draw, then that would be good to see.

There are some power figures at [H] but they include the whole system as well.

Edited May 22, 2007 by jammin

[Verran]

As I said, I was curious about my own system, so an hour or so of data collection from my trusty Kill-A-Watt yielded this:

 

System:

Opteron 148

DFI LanParty SLI-DR (w/ Evercool VC-RE)

eVGA 7800GT (470/1100 stock clock)

2x1GB OCZ DDR500 3-4-4-8

2x80GB Hitachi SATA in Raid-0

4x12" UV CCFLs

2x4" UV CCFLs

~20 UV LEDs

4x120mm Fans (2 Panaflo L1s, 2 Tt low CFM)

2x92mm Fans (both Tt low CFM)

Pioneer 16x DL DVD-R/W

Tagan 480W PSU

 

Settings:

Stock -> Just that, stock speeds and voltages all around.

280x10 -> My "summer" settings. 280x10, 1.35 vCore, 3-4-4-8-1T 1:1 (2.82v), Chipset @ 1.6v, LDT @ 1.3v

300x10 -> Max rock-stable speeds. 300x10, 1.6 vCore, 3-4-3-5-1T 9:10 (2.82v), Chipset @ 1.6v, LDT @ 1.3v

 

(Also note, this system is watercooled. The pump is an Eheim 1250, which as AC powered. Therefore, the pump does not contribute to these figures.)

These numbers are the MAXIMUM draws I could record at any time over the tests. These figures assume a 80% efficiency rate in converting AC to DC. I couldn't find the exact figure for my PSU (even from Tagan's own spec sheet), so I assumed high, to account for maximum draw.

 

In case you don't wan to go over the whole chart, the highest AC draw (at the wall) was 326W in a game test at my highest OC settings with OCCT running a stress test in the background. In DC (which is what PSU ratings actually refer to), that's only 260W!

[jammin]

I would probably call 80% efficiency pretty optimistic as well.

 

I think that's a pretty good addition to the evidence.

 

Do you have the U01?

I will try and dig up some efficiency figures if I can.

Edited May 22, 2007 by jammin

[road-runner]

Well anyway its already shipped and I should not have to buy another PSU for a long, long, time. As far as that review on the 2900 I already new it cost more and used more power for lower quality but it does two things that I wanted that nvidia doesn't, vivo and folding.

[Fireonice]

Well its good to hear my 500w might last longer than i thought it would