5970 psu reqs and question

GJ02 · 18 Nov 2009 at 18:36

hi guys
what sort of power draw are we talking with these 5970's ?
would a corsair 750 do the job ?
are these cards going to blow my 295 out of the water, is it worth waiting for new nvidia cards or is this the one to get ?

muon · 18 Nov 2009 at 18:41

Uses less power than the gtx 295. So if your system can handle that it should be fine.

http://www.anandtech.com/video/showdoc.aspx?i=3679&p=16

edit: whoops, looked at idle only

load is 69w more than the 295.

Greebo · 18 Nov 2009 at 19:24

Problem isn't so much as the total power but how much for each pci-e connector.

I think I read somewhere today that it's 20a on the 8 pin and 16 amps on the 6 pin.

I know a lot of psu's which only put 18amps or less down each 12v line.....

And it wasn't so long ago everybody was laughing at people buying 600W+ psu as being overkill and not necessary........

If it's the TX then it has one single rail so you will be fine.

Ryan-3 · 18 Nov 2009 at 19:41

would an HX750W be fine?

and how big are these exactly, 12 inch + ?

Ritsugamesh · 18 Nov 2009 at 19:49

750w should be fine, as said above make sure to check the amps on each rail to be 100% though.

As for blowing the 295 out of the water, I've not seen a single benchmark where it doesn't outperform the 295 by at least 20%. There is a thread with a fair few benchmarks in these forums, go take a look or just use google.

Kasc · 18 Nov 2009 at 20:03

I have a modular 620W one, will that run it? :O I only have 1 HDD and 1 optical drive.

Greebo · 18 Nov 2009 at 20:07

total power, yes but check your individual rails though.

Spazzfish · 18 Nov 2009 at 20:10

isn't the 750hx one 50a rail?

looks like its up to 62a

http://www.corsair.com/products/hx750/default.aspx

GJ02 · 18 Nov 2009 at 20:47

no, silly thread i started here
i dont need one, ive got a 295 with more than does the job, im only going to convince myself i need one and then get into the wifes bad books
im gonna wait till the green team offer their new offspring and see whats what then

PrincessFrosty · 18 Nov 2009 at 22:11

Greebo said:
Problem isn't so much as the total power but how much for each pci-e connector.

I think I read somewhere today that it's 20a on the 8 pin and 16 amps on the 6 pin.

I know a lot of psu's which only put 18amps or less down each 12v line.....

And it wasn't so long ago everybody was laughing at people buying 600W+ psu as being overkill and not necessary........

If it's the TX then it has one single rail so you will be fine.

This is a recomendation from AMD when overclocking

For overclocked operation, AMD is recommending a 750W power supply, capable of delivering at least 20A on the rail the 8pin plug is fed from, and another 15A on the rail the 6pin plug is fed from. There are a number of power supplies that can do this, but you need to pay very close attention to what your power supply can do. Frankly we’re just waiting for a sob-story where this card cooks a power supply when overvolted. Overclocking the 5970 will bring the power draw out of spec, its imperative you make sure you have a power supply that can handle it.

source: http://www.anandtech.com/video/showdoc.aspx?i=3679&p=4

I'm hoping that good brand name PSUs like Antec will stretch its max rated 18A to 20A.

muon · 21 Nov 2009 at 13:10

I don't understand why you would need so many amps anyway.

75w or 150w through the pci-e slot. Lets say 75w.

20A + 15A at 12v is 420w. So thats a total of 495w.

Unless you do some crazy overclocking, I'd be surprised if you get that much of an increase from the 294w tdp.

^JP^ · 21 Nov 2009 at 13:37

My PSU has this on the side

So both 8pin PCI have 28A and both 6pin have 18A

Enough to run 2x 5970s (when I get a 2nd) and plenty of headroom to overclock.

Plus no matter how I load this PSU it never gets loud :cool:

I highly recommend one of these Zalmans!

muon · 21 Nov 2009 at 13:42

The thing about that PSU is that all those rails cannot simultaneously run at the amps they've rated them at.

[(4 x 18A) + (2 x 28A)] x 12V = 1536W.

Yet the max combined wattage for the 12V rails is 960W. I hate when PSU manufacturers do that.

Compare that to single rail PSUs, where the amps rating is the same as the max wattage.

70A x 12V = 840W

If ATI recommend 495W on 12V rail for each overclocked card, as mentioned in my post above (something which I think is way over the top), then your PSU doesn't actually suffice.

Then theres your CPU using power off the 12V rail as well.

^JP^ · 21 Nov 2009 at 13:56

Thats makes sense, thanks for the info.
I guess if I have problems when I get a 2nd card I can always put the PCP&C back in thats got 100A single rail but makes a hell of a noise all the time

Really need some accurate data on just how much power is required.

Edit:
Just looking here http://www.amd.com/us/products/desk...s/ati-radeon-hd-5970-system-requirements.aspx

For Crossfire 5970 it says "850 Watt with two 75W 6-pin and two 150W 8-pin"
So is that 6.25A and 12.5A ?

muon · 21 Nov 2009 at 14:24

^JP^ said:
Thats makes sense, thanks for the info.
I guess if I have problems when I get a 2nd card I can always put the PCP&C back in thats got 100A single rail but makes a hell of a noise all the time

Really need some accurate data on just how much power is required.

Edit:
Just looking here http://www.amd.com/us/products/desk...s/ati-radeon-hd-5970-system-requirements.aspx

For Crossfire 5970 it says "850 Watt with two 75W 6-pin and two 150W 8-pin"
So is that 6.25A and 12.5A ?

Exactly. 75w from motherboard + 225w from pci-e power connectors results in 300w satisfying the 294w tdp.

I don't understand why overclocking it would require the amps mentioned in the anandtech article.

To hit 495 watt,

You would have to max out the volts 1.1625v (I'm assuming stock volts are 1.05v, but I'm not certain) and also overclock it to ~1000mhz.

{[(1.1625/1.05)^2]*[1000/725]}*294W = 497W

^JP^ · 21 Nov 2009 at 14:35

Ok well thanks for all the info. Very helpful!

fornowagain · 21 Nov 2009 at 14:54

ghost101 said:
I don't understand why overclocking it would require the amps mentioned in the anandtech article.

To hit 495 watt,

You would have to max out the volts 1.1625v (I'm assuming stock volts are 1.05v, but I'm not certain) and also overclock it to ~1000mhz.

{[(1.1625/1.05)^2]*[1000/725]}*294W = 497W

Yeah 1.05v is the default. Seems there's a few people hitting 1000Mhz so the 495W isn't that far fetched. Although the power equation isn't strictly accurate, you'd need the TDPs for the separate clock domains of core and memory. And of course the card isn't using anything like TDP in actual use. I'd guestimate nearer 400W at 1000MHZ/1.1625v. But it does illustrate how fast the power usage rises.

http://www.anandtech.com/video/showdoc.aspx?i=3679&p=16

Looking at the 5970 when it’s overclocked, it becomes readily apparently why a good power supply is necessary. For that 15% increase in core speed and 20% increase in memory speed, we pay a penalty of 113W!

---------------------------

A few users getting 1000Mhz on air, assume high Vgpu.

http://www.xtremesystems.org/forums/showthread.php?t=239355
http://www.xtremesystems.org/forums/showthread.php?t=239397
http://www.xtremesystems.org/forums/showthread.php?t=239370

TAC4U · 21 Nov 2009 at 15:32

fornowagain said:
Yeah 1.05v is the default. Seems there's a few people hitting 1000Mhz so the 495W isn't that far fetched.

Hitting 1000Mhz would be pretty beasty.

Antx777 · 21 Nov 2009 at 18:47

Got a 850 watt OCZ Gamestream currently running GTX8800 in SLI/QX9650 @3.8 this would run a 5970 yes? (20amps on easch of four rails) - just wondering, as i thought, at firsrt that the 5970 was very low on power consumption, lower than a 295 for example.....

~Ant

TAC4U · 21 Nov 2009 at 20:21

Antx777 said:
as i thought, at firsrt that the 5970 was very low on power consumption, lower than a 295 for example.....

Nope, definitely higher on load. But the complete system load for an overclocked 5870 shouldn't be more than 700W, so you shouldn't have an issue. Still, I went for a 1000W PSU just to be safe, as my overclocked i7 draws quite a lot of power.