PSU Power

masscrazy · 15 Jan 2012 at 21:49

Is the AX850 enough to go 6990/6970.

Considering the 7970 and then another or 7990 late down the line.

Surely 6990/6970 will use more power so wondering if for the new 7000series tri-fire the AX850 will be enough.

beejjacobs · 15 Jan 2012 at 21:51

For tri-fire no. But for crossfire yes!

spain · 15 Jan 2012 at 22:10

Check this review page8 gives full system stress power consumption of their test system =355 watts, if the 7990 uses "350-400" watts thats only 755-800 watts max. That AX psu should have a 100-150 watts headroom, (check reviews), so should be ok.

Personally I would not want to stress the psu and would upgrade the psu for more headroom for overclocking the cards etc.

The best way to check is buy a cheap meter that tells you the power draw of your system from the wall.

masscrazy · 15 Jan 2012 at 22:12

Corsair 1050HX, similar price to the AX850

RJC · 15 Jan 2012 at 22:14

Looking at review for the 2 older cards the 6990 at full load including system pulls 434w and 137w idle, the 6970 pulls 340w full load and 161w idle.

The 6990 would pull 297w and the 6970 would pull 179w so this would be 476w with the GPU'S at stock so in theory you would be pulling 632w with the gpus at load.

spain · 15 Jan 2012 at 22:24

The figure I gave for the 7990 at 350-400 watts is way to high, might be below 300w, we will know in due course.

Reaper 392 · 15 Jan 2012 at 22:33

750W is the usual OcUK recommendation for two 6970s in crossfire, so i'm going to recommend you get something ~950W for what is effectively 6970 tri fire

masscrazy · 15 Jan 2012 at 22:47

OK so basically 850W is not enough for tri-fire 6990/6970. Therefore not enough for 7990/7970 tri-fire?

spain · 15 Jan 2012 at 23:04

That AX psu has a max load of 1045w check here, and should operate at 900w very well, that's some serious headroom built in, real quality psu. It's all about the noise level once you go over 60% of the 850w.

Get the cards and a meter and try it, if it uses 750w or less keep it, if not change. obviously you cant get the 7990, so get the 7970 see how it goes if you fancy those cards.

Edit:
Just a thought I for some reason assumed your already got the psu If not then get something better.

masscrazy · 15 Jan 2012 at 23:12

spain said:
That AX psu has a max load of 1045w check here, and should operate at 900w very well, that's some serious headroom built in, real quality psu. It's all about the noise level once you go over 60% of the 850w.

Get the cards and a meter and try it, if it uses 750w or less keep it, if not change. obviously you cant get the 7990, so get the 7970 see how it goes if you fancy those cards.

Edit:
Just a thought I for some reason assumed your already got the psu If not then get something better.

Corsair 1050hx then. But i'd like one that is efficient and fan off when idling.

beejjacobs · 15 Jan 2012 at 23:22

Are you sure you want tri-fire? What res do you run at?

spain · 15 Jan 2012 at 23:23

At 731rpm under 50% load it should be silent, your other fans will be louder. It Looks like a sound psu and would do the job, read some reviews and see how it holds up under stress. Corsair is a good make but there's others out there which might be worth looking at.

I don't think I would worry about how efficient the psu is, your looking at quality kit they are all efficient. Converting an extra 10-30w drawn from the plug in to usable energy is great an all, but with the system your thinking about, lol.

Psyisk · 15 Jan 2012 at 23:35

get 750 w corsair and be done

rowedogg · 15 Jan 2012 at 23:42

i thought 7xxx were less power hungry?

masscrazy · 15 Jan 2012 at 23:45

beejjacobs said:
Are you sure you want tri-fire? What res do you run at?

2560x1440 - tri-fire quite possibly yes.

Psyisk said:
get 750 w corsair and be done

That wont run 2 7970s let alone a tri-fire setup.

Also according to the link spain gave, the ax850 gave a max of 1045W. Hmmm what to do....

spain · 15 Jan 2012 at 23:45

rowedogg said:
i thought 7xxx were less power hungry?

Well we don't know about the 7990, but it should be. Its when you start overclocking hard that you will need lots of headroom.

spain · 15 Jan 2012 at 23:58

masscrazy it's a tough call, the AX850 really is nice, but most will tell you to play safe and get a higher rated psu.

The last resort (you seem set on this psu) is to get the AX850 with one card if the 7970 and test it overclocked hard, see what the power draw is and what headroom you have left. If it falls short then send it back within 7 days and replace it.

masscrazy · 16 Jan 2012 at 00:01

spain said:
masscrazy it's a tough call, the AX850 really is nice, but most will tell you to play safe and get a higher rated psu.

The last resort (you seem set on this psu) is to get the AX850 with one card if the 7970 and test it overclocked hard, see what the power draw is and what headroom you have left. If it falls short then send it back within 7 days and replace it.

Not quite sure you can send it back once its been used like that.

Though I've seen the ax850 for £139.99 which is cheap, if it doesnt work out to be enough I guess selling it wouldnt be so bad, i'm sure I could get what I pay for it.

spain · 16 Jan 2012 at 00:16

That's an option if your set on that psu, it's a gamble, but your clearly aware of that, so good luck with whatever you decide.

beejjacobs · 16 Jan 2012 at 00:24

RJC said:
Looking at review for the 2 older cards the 6990 at full load including system pulls 434w and 137w idle, the 6970 pulls 340w full load and 161w idle.

The 6990 would pull 297w and the 6970 would pull 179w so this would be 476w with the GPU'S at stock so in theory you would be pulling 632w with the gpus at load.

This tells you a lot. 850W will be plenty for Crossfire 7970. and probably 7990+7970 should you ever want to!