power supply to power 2 2900 XT 1GB

RaiderX · 2 Jul 2007 at 01:51

i am thinking of getting 2 2900 XTs in crossfire as my new mobo supports it and i have the cash for it, but i dont think my thermaltake purepower 680w would be upto the job of powering 2 of the beasts.

it needs to fit into an antec p180 case so cant be too long.

Cyber-Mav · 2 Jul 2007 at 02:43

your current psu should be ok for the job.

fornowagain · 2 Jul 2007 at 03:52

The psu's ability to power that dual card system is mainly based on its 12v combined current. Unfortunately TT don't give the combined value, only the separate rails. Which in 9/10 cases can't just be added together. The worry is if you look at the specs for the TT 680W its got massive 5v/50A & 3.3v/28A rails. Do the math, take the worst case its 337W/28A or best case (12v summed) 456W/38A. Its probably somewhere in between, 400W/33A.

Two 2900XT are going to use anything from 300W to 350W and even more overclocked. You may well get away with it, but looking at that system it wouldn't be hard to get close or past the 12v rail limit.

A more modern psu, even with a smaller overall wattage like the Corsair 620W has much larger 12v rails, 600W/50A.

http://www.overclockers.co.uk/showproduct.php?prodid=CA-004-CS&tool=3

hp7909 · 2 Jul 2007 at 06:23

Those Corsair's are really impressive. 50A is just 4 less if all the +12V rails were added :eek:

Maybe they should advertise their PSU with +12V Amperage instead of Watts. How many times have we heard 'will 620Ws be enough'

eracer2006 · 2 Jul 2007 at 06:32

would 2 1gb 2900xt's be better than 1 8800 ultra ?

Explosivo · 2 Jul 2007 at 09:33

eracer2006 said:
would 2 1gb 2900xt's be better than 1 8800 ultra ?

i would think so

HeX · 2 Jul 2007 at 09:40

So you know those 680W Tt Purepowers are rubbish for SLi or Crossfire, their 12V output is dire.

I used to have one and it couldn't even power 2 x 7800GT's in SLi, used to bluescreen or hard reset when the cards started to draw too much power.

I replaced it with a 600W OCZ (supposidly 80W less than the Tt) and never had a problem again.

If you have a look round the web you'll find out how bad that 680Tt actually is, its main letdown is that its 12V rails are tied to the 5V rails, so you have to ballance the load, the 12V's can't draw as much power until the 5V rail is heavily loaded, its really dodgy.

SinaiSound · 2 Jul 2007 at 10:49

The corsair HX620 is an excellent buy and would suit your needs well.

You'll also need a 64bit operating system in order to address that much video memory; which is another consideration

Cyber-Mav · 2 Jul 2007 at 10:54

thats odd, when i checked thermaltakes website the purepower 600w has got 48amps on the 12v rails so i thought the 680w should be more than enough. :confused:

http://www.thermaltake.com/product/Power/PurePower/w0144/w0144.asp
:confused:

Nullvoid · 2 Jul 2007 at 11:09

You're looking at an RX model though which is a reintrodced and considerably buffed up version.

LoadsaMoney · 2 Jul 2007 at 11:52

12v rail is way to low on there for 2x 2900's in Crossfire id have thought, those cards need an unbelievable amount of power, a single 2900 uses more power than a GTX.

fornowagain · 2 Jul 2007 at 13:49

Cyber-Mav said:
thats odd, when i checked thermaltakes website the purepower 600w has got 48amps on the 12v rails so i thought the 680w should be more than enough.
http://www.thermaltake.com/product/Power/PurePower/w0144/w0144.asp

That's a very different beaste.

RaiderX · 2 Jul 2007 at 14:30

might get http://www.overclockers.co.uk/showproduct.php?prodid=CA-001-PP&groupid=701&catid=123&subcat=928 when there in stock, says certified for crossfire 2900 XT

fornowagain · 2 Jul 2007 at 14:43

RaiderX said:
might get http://www.overclockers.co.uk/showproduct.php?prodid=CA-001-PP&groupid=701&catid=123&subcat=928 when there in stock, says certified for crossfire 2900 XT

Very nice, that's the one I'd buy if I was upgrading. Didn't know OcUK now stocked them.

chaparral · 2 Jul 2007 at 17:57

Kanifee · 3 Jul 2007 at 00:07

so would these numbers be fine to oc a 8800gts on im very noobish on psu's and i was a little worried as i only spent £38 on this and i see u guys spending £80+

600 watt

+5v +3.3v +12v 1 +12v 2 +12v 3 -5v -12v +5vsb
34a 30a 18a 18a 16a 1a 1a 3a

last time i purchased a psu i had 20a on the 12v rail and only one rail

sorry for jumping in just thaught it had relavance

helmutcheese · 3 Jul 2007 at 00:17

IMO best you can get:

http://www.enermax.co.uk/products/psu/infiniti/index.asp

All rails are solid at + values with a multimeter on full load for ram/gpu/cpu fully heated up. (tested today).

" Satisfy your infinite desire

Dual CPU . Quad Core . Triple GPU

18 Hard Drives . EPS12V 2007 support "

Nullvoid · 3 Jul 2007 at 01:05

damian666 said:
so would these numbers be fine to oc a 8800gts on im very noobish on psu's and i was a little worried as i only spent £38 on this and i see u guys spending £80+

600 watt

+5v +3.3v +12v 1 +12v 2 +12v 3 -5v -12v +5vsb
34a 30a 18a 18a 16a 1a 1a 3a

last time i purchased a psu i had 20a on the 12v rail and only one rail

sorry for jumping in just thaught it had relavance

What brand is it damian? A psu with three quite highly rated 12v rails at only £38 seems like a right bargain!

helmutcheese · 3 Jul 2007 at 01:10

Q-TEQ Gold 650

Kanifee · 3 Jul 2007 at 01:46

its a works power reactor 600watt
never heard of them but tonight i spotted one on an american site taged at just over $160
wich was a pleaseant surprise my thinking is bloke gave me wrong one for less money as its in the wrong box was in a high point box
one of them proberbly trying to fiddle and purchase a cheap one with a diffrent one in the box lol.