Do I have enough power for crossfire-goodness?

Hussman · 20 Mar 2006 at 16:10

Hi,

I'm hoping to run an ATi x1900xt mastercard with a Sapphire x1900xt-x slave.

My power supply is a Hiper 580W lump.

Will I be able to do it, or will I need a mini-nuclear reactor to power these beasts?

Thanks

Hussman

PS : Rest of my PC is in my sig, on the right.

Bennah · 20 Mar 2006 at 16:13

Should be ok, but I havnt heard any experience's with a Hiper 580w psu though on a CF setup though.

The cards would need a lot of power. Weather the psu is upto the job, Im unsure. Dont know what these psu's are like.

I do know that the Tagan U22 580w SLI psu is a great psu for the job and extremely well priced too.

oweneades · 20 Mar 2006 at 16:28

My old Hiper 580w worked fine for SLI's 7800GTX's although crossfire I don't know.

Coolasmoo · 20 Mar 2006 at 17:13

Hussman said:
Hi,

I'm hoping to run an ATi x1900xt mastercard with a Sapphire x1900xt-x slave.

My power supply is a Hiper 580W lump.

Will I be able to do it, or will I need a mini-nuclear reactor to power these beasts?

Thanks

Hussman

PS : Rest of my PC is in my sig, on the right.

If its the one im thinking (type r)

Then they have 20a + 18A = 38 which is the recommended spec for X1900 Crossfire.

Im running the Seasonic 600w and its 18 +18

I have tried my hiper PSU also, and it runs fine

Bennah · 20 Mar 2006 at 17:15

Tagan U22 580w SLI - £73.97

3.3v @ 28A, 5v @ 48A and 2x 12v lines @ 20A each...

Hiper Type R 580w - £62.22

3.3v @ 30A, 5v @ 36A and 2x 12v lines @ 20A / 18A...

For the extra £11.77, Id go with the Tagan

Its a great psu, mate of mine swears by it using CF and SLI setup's to other psu's like the OCZ powerstream 600w that he has tried out the in the past.

Hussman · 20 Mar 2006 at 17:21

Thanks for all the input.

I already have a type r and don't really want to buy another PSU.

Looks like I should be ok then?

Thanks again.

Hussman

pastymuncher · 20 Mar 2006 at 19:39

You do realise that the XT-X will throttle back to the XT speed so you might be better off getting two XT's. Just a thought.

Nothing wrong with the Type R. I have one powering my rig and it has never let me down and is also very quiet, silent even.

Coolasmoo · 20 Mar 2006 at 20:13

pastymuncher said:
You do realise that the XT-X will throttle back to the XT speed so you might be better off getting two XT's. Just a thought.

The XTX will run at its normal speed

I dont know where you got your info from

Bennah · 20 Mar 2006 at 20:34

I know, that info came about from somewhere and everyone is under the impression that it does but it does'nt.

Hussman · 20 Mar 2006 at 22:06

Hi,

Can you please clarify, will it throttle back to XT speeds, or will it run at xt-x speeds?

I've heard many, often conflicting, reports about this.

Thanks

smids · 20 Mar 2006 at 22:23

It will run @ XT-X. The only time anything throttles is if there is a different amount of RAM or they have a different number of pipelines e.g. X1800XT Master + X1800GTO.

They will always run at their speed. They only change when pipes/RAM amount is different to summise

.

Hussman · 20 Mar 2006 at 22:27

Great, so basically an x1900xt mastercard and an x1900xt-x slave will be better than an x1900xt mastercard and an x1900xt slave?

smids · 20 Mar 2006 at 22:37

Yes, but not by much. The clocks are so close you might just as well get two XT's and clock them.

Hussman · 20 Mar 2006 at 22:38

So if I ran them at stock (no overclocking) would I see any "real world" difference?

What about a "guestimate" at the increase in 3dmark 06?

Thanks in advance.

smids · 20 Mar 2006 at 22:46

Guesstimate umm.... 50 points, if that, at stock?

Hussman · 20 Mar 2006 at 22:47

So do you recommend me saving the £30 and getting the XT slave card and putting the saving towards the new Zalman vf900 cooler?

smids · 20 Mar 2006 at 23:56

Yeah, I'd say so. The XT-X only really comes into it on its own as they clock very well but when overclocking an X-fire, you clock them at the same time meaning you are always limited by the XT clocks (I think this is how it works, someone correct me if I'm wrong).

S_D · 21 Mar 2006 at 01:00

Don't forget thought that the XT-X will have 1.1ns RAM and a lot of XT's now will have 1.2ns meaning they won't clock as well. I suspect the GPU's on the XT-X are better chips too.

If you want confirmation of the independant speed fact about the cards then check ATI's crossfire pdf on www.ati.com.

Simon

fornowagain · 21 Mar 2006 at 02:58

To get some idea of your systems load plug your devices in this calculator.

http://www.extreme.outervision.com/index.jsp

An article on CF/SLI worth reading.

http://www.extremetech.com/article2/0,1697,1932947,00.asp

512MB gaming cards in SLI/CrossFire will pull anywhere from around 15A to slightly over 20A (taking 120W divided by 12V = 10A per card) meaning that our +12V3 rail was overloaded as it has to share the power draw from the motherboard as well (which typically draws around 2 ~ 3A on its own). Since we rate our power supplies conservatively, the ST60F could actually run Kelt's 7800GTX 512MB SLI system for a while despite being technically overloaded on the +12V3 rail. As soon as the over current protection point of 20A on the +12V3 is reached, the power will automatically shut down.

And a short but useful guide to the PSU requirements for CF/SLI

http://jonnyguru.com/findingtherightpsu.html
http://jonnyguru.com/psu2.html

Confused about Dual Rails? This may help with the usual misconceptions.

http://forums.silentpcreview.com/viewtopic.php?t=23916
http://www.silentpcreview.com/article28-page1.html

It's important to remember that even though there are two "independent" 12V lines, they still draw from the same main source. It's highly unlikely that there are two separate 120VAC:12VDC power conversion devices in a PSU; this would be much too costly and inefficient. There is only one 12VDC source, and the two lines draw from the same transformer. Each line is coming from the same 12VDC source, but through its own "controlled gateway".

PSU makers' specs are misleading in that thay rate the current capacity of each 12V rail independently. What really matters is the total 12V current: Generally, up to 20A is available on any one 12V line assuming the total 12V current capacity of the PSU is not exceed.

Rememer to look for the total combined wattage for the 12v outputs. Don't just add the two rails together, you may not be getting as much as you think you are!!!!

http://www.tomshardware.co.uk/2007/03/27/pci_express_scaling_analysis_uk/page4.html
http://www.smpstech.com/tutorial/t00con.htm

Hussman · 21 Mar 2006 at 17:20

Thanks for taking time to explain it all.

Cheers everyone!

Hussman