Question on ATI PSU Requirements

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pypeters

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I plan on buying a 1900XT for my new system but I'm a little confused on the suggested power requirements. From what I have gathered it is a good idea to a PSU capable of over 24A or higher on the 12V line. What is confusing me is that some of the ATI approved PSU only have 18A for each 12V line (eg 12V1/18A, 12V2/18A). Does this mean the PSU really has 36A available for single 12V line connection and if you use crossfire then there would only be 18A each?

Any information would be great, thanks.
 
The recommended 24a is a combined rating...18a on each 12v rail is fine. There are other things that require the 12v so that is why they recommend 24a combined. If you think you might want to go crossfire in the future make sure your psu is rated for it...some non-SLI psu's work fine for SLI but Crossfire is known to blow psu's that aren't certified.
 
The X1900XT card doesnt need the full 24 amps, that is the spec for the whole PC system.

The power supply with 2 x 12V rails at 18A each will be fine for one card.
Use one rail for the graphics card and the other rail for anything else.
 
You'll be fine with that PSU, it says it supplies 16A on each of the two +12V lines. It will work, I got my x1900xt in yesterday and hooked it up to a Antec TruPower 2 430W, no problems what so ever.
 
What you get from ATi and boards is borderline insane. ~30 amps a card. So i just got a corssfire approved psu. A relatively cheap Sparkle 650w. It gives my two cards the juice that lets them kick ass and take names. Energy in, heat out, it lets them get their flame spitting grove on.
 
I'm sure that they specify 24A for the whole system with one card in.
Once card takes way less than 20A, I'd find out exactly for you but I just woke up :)
 
It seems the spec for the whole system for an X1900XT is 30A not 24A (I've had a coffee now :)).
I found an interesting article. On this page:
http://www.xbitlabs.com/articles/video/display/powercolor-x1900xt_3.html
they talk about the individual power used by the cards components

"Graphics cards of the Radeon X1900 family have high power consumption, and we were curious to know how big a share the high-frequency memory has in this. We read through the tech specs of the K4J52324QC series and found that the BJ12-suffixed chips have a peak consumption of 1.195A. Working at 2.0V voltage, each chip thus consumes 2.39W. So, all of the graphics memory on board the Radeon X1900 XT consumes a total of about 19W. It also means that the graphics processor of the card consumes as much as 89W which is very high and comparable with the consumption of such processors as AMD Athlon 64 X2 4800+! The Radeon X1900 XT GPU consumes even more – 100W almost! Since the power consumption of the memory chips is rather low, the use of elastic thermal pads is quite justifiable, although they are rather too thick to be very effective."

Total power of just the IC's is 119W which is 10A.
Add on another 30% for other components and extra to be safe gives 155W.
Even with figures this high, each card uses only 13A.

The HE 430W PSU used in the Antec P150 case is described on this page:
http://www.case-mod.com/store/antec....html?osCsid=867a07e105d4892973c14ce125cb1271
The alignment of the table is messed up (on my display).
If it looks just as messy on yours, the 3 x 12V rails each can supply 16A (confirmed by Anti-Hero) so it is good for the job of powering Crossfire!
 
Hey, thanks for the swift replies, everyone.

I didn't know that this PSU would be good enough for Crossfire. For the time being, I'm only going to be running one GPU, an IDE DVD Drive, a SATA HDD, plus a Core 2 Duo (overclocked, but to what extent I don't yet know). My mobo won't be Crossfire-compatible, but it's nice to know that my PSU should be quite future-proof.
 
cool :)
be sure to use seperate power rails for each graphics card and the system.
It should trip the PSU (with no damage) and not power up if you get it wrong.
 
Sorry to sound so dumb, but what exactly is a 'power rail'? Without knowing what you're talking about, I can't picture what I am and am not supposed to do, and it sounds serious.

I will, of course, read the manuals properly.

Just FYI, I'm building a new system from scratch, migrating from a Socket A build, so anything technical beyond that is, well, beyond me.
 
Think of your PSU as having 3 mini PSU's built into it.
The leads attaching to each mini psu should be labelled in some way so you can identify them.

A power rail is one voltage line. ie 12V is one power rail, 5V is another.
In your PSU you have 3 x 12V power rails, each should have its own lead or leads.
 
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