If anyones wondering what 3x 7970s draw in a watercooled rig...

Stu @ MSD · 11 Mar 2012 at 12:50

Hi everyone,
I have read all sorts of power figures for a trifire 7970 setup in mags and on websites so decided to buy my own meter and measure it myself to ensure PSU was not causing any bottlenecks here, so the answer is....

Tests were:

Heaven 2.5 @ 1920 x 1080 with everything at full and that never saw in excess of 850w.

3D mark 11 on extreme didnt exceed 935.

3D mark vantage interestingly was the one that will repeatedly peaked at almost a kw on the return to jerico scene.

Rig of course is totally relevant, so here it is:
Mobo: Asus Maximus Extreme IV - Z
CPU: Intel Core i7-2600K
GPU: 3 x Sapphire Radeon 7970's
RAM: 16GB of Corsair Vengeance 1866MHz
SSD: 2x OCZ Vertex 3 Sata 6 SSD
HDD 2x 1TB Western Digital Velociraptors
PSU: XFX Pro 1250w Black gamer Edition
Optical: Pioneer 12x Blu Ray Combo Drive
Pump: Alphacool VPP655 - D5 Pump
Fans 120mm: 3 x Scythe Gentle Typhoon 1850RPM - AP15s on the radiator.
fans 140mm: 3x Corsair 140mm fans around the chassis.
Lighting: LED's and a UV inverter so far.

Just thought it may help people in future who are wondering the same thing.

Eyefinity testing at 5760x1200 in battlefield three with all settings at ultra will be the next test... if we ever get a driver that lets me run trifire with BF3.

**Edit**
Sorry, to add, the CPU is running at 5.2ghz and the GPUs all at 1125 with ram @ 1575

panyan · 11 Mar 2012 at 12:53

pics of rig please

sehcure · 11 Mar 2012 at 12:57

panyan said:
pics of rig please

This!

Interesting stuff; I have seen figures from a conservative 700w to over 1300w quoted in various places so top job OP

Stu @ MSD · 11 Mar 2012 at 13:02

panyan said:
pics of rig please

sehcure said:
This!

Interesting stuff; I have seen figures from a conservative 700w to over 1300w quoted in various places so top job OP

Me too, was constantly wonderuing if some of my overclocking walls were due to inadequate PSU so just had to find out once and for all. Well worth £20!

Build info here:
http://forums.overclockers.co.uk/showthread.php?t=18381447

stulid · 11 Mar 2012 at 13:02

Remember to account for the PSU efficiency (Gold for that one) so its roughly 90% of that figure that the parts are sucking from the PSU.

Stu @ MSD · 11 Mar 2012 at 13:09

stulid said:
Remember to account for the PSU efficiency (Gold for that one) so its roughly 90% of that figure.

Whilst I totally understand what you are saying, N-Power would disagree with you come bill time. In the real world, the "PC" as a whole, is consuming 991W peak.

However, if you get a more efficient PSU, say 90%, yes, you could tweak that figure down somewhat to maybe 900w.

Krony · 11 Mar 2012 at 13:16

Try 3DMark11 on P preset plz, that is where i recorded my peak usage of around 900w if i remember correctly with sli 580's, the P preset ran higher wattage than X preset.

booterboy · 11 Mar 2012 at 13:21

That is a really impressive rig,sick with envy.
If you can afford a build like that Im sure the electriciy bill is of no concern lol.
Great to see a member posting real results of psu use.
Again,smashing setup.

MichaelM · 11 Mar 2012 at 13:28

Try Crysis 2 and see if you get over 1000!

rare · 11 Mar 2012 at 13:29

I think you might be lacking power in the GPU department

Surveyor · 11 Mar 2012 at 13:31

Stu @ MSD said:
However, if you get a more efficient PSU, say 90%, yes, you could tweak that figure down somewhat to maybe 900w.

Your PSU is Gold rated so should operate at approaching 90% efficiency at high loads.

The PSU is only outputting around 90% of what you see at the mains so only around 900W of its 1250W at the highest reading you've recorded.

But it's still drawing close to 1000W from the mains at your highest reading and that's what you'll be paying for.

Stu @ MSD · 11 Mar 2012 at 18:57

booterboy said:
That is a really impressive rig,sick with envy.
If you can afford a build like that Im sure the electriciy bill is of no concern lol.Great to see a member posting real results of psu use.
Again,smashing setup.

Thank you.

MichaelM said:
Try Crysis 2 and see if you get over 1000!

Trying exactly that tonight.

Surveyor said:
Your PSU is Gold rated so should operate at approaching 90% efficiency at high loads.

The PSU is only outputting around 90% of what you see at the mains so only around 900W of its 1250W at the highest reading you've recorded.

But it's still drawing close to 1000W from the mains at your highest reading and that's what you'll be paying for.

Yeah, I do totally understand you mate, For the purpose of this topic I am trying to report the electricity used by the PC as opposed to the energy actually used by the PC components themselves after the PSU.

Zeed · 11 Mar 2012 at 20:21

i would say that BF3 should take most tbh. Its only game taht makes my gpu overheat :/

Crezzlin · 21 Mar 2012 at 19:03

Have you had BF3 on Trifire yet? i have 2 7970's and would like a 3rd if it works?, i play @ 5760x1200 and have your psu

Sin_Chase · 21 Mar 2012 at 19:05

That is a huggggge draw!

Go for a kiloWatt!

uk_unbeliever · 21 Mar 2012 at 19:17

stulid said:
Remember to account for the PSU efficiency (Gold for that one) so its roughly 90% of that figure that the parts are sucking from the PSU.

A quick question about this- in terms of making sure a PSU is up to the job, do you need to look at the 'at the wall' measure? I.E. in this case 991W, meaning a 1kw PSU would be cutting it very fine, or would a 1kw 90% efficiency PSU technically be ok up to 1100w (at the wall measurement)?

xsistor · 21 Mar 2012 at 20:12

Stu @ MSD said:
Whilst I totally understand what you are saying, N-Power would disagree with you come bill time. In the real world, the "PC" as a whole, is consuming 991W peak.

However, if you get a more efficient PSU, say 90%, yes, you could tweak that figure down somewhat to maybe 900w.

Point he was making was that 991w wasn't the power the PSU needs to source. Calculating that gives you a figure you can use to spec PSUs independent of the PSU efficiency.

Sin_Chase · 21 Mar 2012 at 20:20

xsistor said:
Point he was making was that 991w wasn't the power the PSU needs to source. Calculating that gives you a figure you can use to spec PSUs independent of the PSU efficiency.

That's not strictly true though surely?

You want to know what power you need to Input to support your load.

If your components draw a true 500Watts your PSU needs to source the 500Watts + the overhead lost outside of it's efficiency rating.

No point speccing a 500Watt PSU for a true load of 500Watts when you need 550Watts to account for a 90% efficiency.

You still need to factor in the losses, they are not 'free'.

Crezzlin · 21 Mar 2012 at 20:22

When i ran 3x 6970's with a Antec 1000w all games would run ok but BF3 would max the power usage out and reboot my pc.. got the xfx1250 and all was ok.

xsistor · 21 Mar 2012 at 20:39

Sin_Chase said:
That's not strictly true though surely?

You want to know what power you need to Input to support your load.

If your components draw a true 500Watts your PSU needs to source the 500Watts + the overhead lost outside of it's efficiency rating.

No point speccing a 500Watt PSU for a true load of 500Watts when you need 550Watts to account for a 90% efficiency.

You still need to factor in the losses, they are not 'free'.

What matters is the DC power your components draw. Not the AC power drawn from the wall, as this can vary for two reasons: 1) power efficiency in terms of thermal losses, and 2) Reactive power vs real power.

I would adjust power drawn from the wall for at least the operational power efficiency before deciding what the components are drawing. That way, say if 991w is on a PSU that operates at 90% efficiency then you use that when speccing for a different PSU which may, for example, have 80% efficiency. In this instance as long as the power the PSU sources is within the range, it's good.