probably retarded, but

[imported_neptune]

By no means am I an electrician, and I am probably restarded, but: Can a PSU (GameXStream 700W) that has 4x 18A 12V rails handle video cards that need one single 30A 12V rail? When not using the other rails is the power distributed? Does the PSU have 72A available in total amongst the 4 cables or is that not how it works? Thanks; be gentle

 

[corkyg]

The specific answer is "yes."

Rails

 

[imported_neptune]

I assume you mean yes, it can handle it. Can anyone elaborate a bit about how this works? Any and all info is greatly appreciated. Thanks

 

[BOLt]

You're not retarded. Quit beating yourself up. It's embarrassing.

Yes, is the correct answer. The rails act in parallel (sp.?) to power your stuff.

 

[imported_neptune]

I only beat myself up once and it hurt, but I don't think anyone saw it; I'm not embarrassed. Thanks for the answer though. You did spell parallel correctly, so I guess you're not retarded either. So, I guess I will be all right so long as I don't fill all 4 rails with products that each require more than a total aggregate of 72A

 

[Skeeedunt]

I don't think any single video card requires 30A on the 12V rail... that just means you should get a power supply with 30A TOTAL in order to use the card.

Also, you can't just add up the rails. 4x18A doesn't necessarily = 72A.

(That PSU is almost definitely overkill for whatever it is you're doing.)

 

[imported_neptune]

The X1950 requires 30A on a 12V rail, look at the website. How does that change your answer? Is this PSU enough when it only has 18A per rail and uses only 1 rail?

 

[jonnyGURU]

Originally posted by: neptune
The X1950 requires 30A on a 12V rail, look at the website. How does that change your answer? Is this PSU enough when it only has 18A per rail and uses only 1 rail?

Look at the website again.

It requires a power supply with at least 30A on the 12V rail... combined. Not one.

ATI is cool with their PSU testing in that they actually test in a real environment (built PC with multiple drives, etc running every benchmark on the face of the Earth.) Really you only need to make sure the PSU has a rail with at least 19A on the 12V rail that supplies juice to the PCI-e connectors. Preferably, a rail that is dedicated for use with the PCI-e connectors.

 

[imported_neptune]

OK, so we got people saying combined, not combined and some other vaguaries. The responses are appreciated, but can we get to a bottom line here; 2+2=4 kinda thing? So, if the GameXStream has 700W, 4 x 12V @ 18A each, will this combine to be enough for the purpose of this card? It will take all necessary juice that is required from the aggregate? How much does this PSU supply on the 12V rail overall? I will only be using the video card, and none of the other 3 connectors, so how much juice does the video get available to it? Thanks...

 

[ElTee]

neptune: if you look here ATI Crossfire Certified PSU's you'll notice that ATI has certified that PSU for use in Crossfire systems, i.e. that PSU will be able to power your vid card.

 

[jonnyGURU]

Originally posted by: neptune
OK, so we got people saying combined, not combined and some other vaguaries.

That's the thing that sucks about going to forums for advice. Most of the advice is incorrect.

Originally posted by: neptune
The responses are appreciated, but can we get to a bottom line here; 2+2=4 kinda thing? So, if the GameXStream has 700W, 4 x 12V @ 18A each, will this combine to be enough for the purpose of this card? It will take all necessary juice that is required from the aggregate? How much does this PSU supply on the 12V rail overall? I will only be using the video card, and none of the other 3 connectors, so how much juice does the video get available to it? Thanks...

If you look on the sticker, right below where it shows all four 12V rails and their capability, there is a 12V combined rating:

http://www.jonnyguru.com/PSU/GameXStream700/IMG_0600.jpg

It's 680W (assuming no load on the 3.3V or 5V.)

So that means your combined 12V capability is 56.6A.

The GameXstream has a "rail" for each PCI-e. 12V3 goes to one and 12V4 goes to another. That means you have 18A available per video card. Full load I don't think each X1950 uses more than 10A.

When ATI suggests 30A, they're taking into consideration you're also going to need 12V for the CPU, drives, fans, etc. So the guestimate is "30A." But it's not that the card needs 30A or that all 30A needs to be on any single 12V rail.

 

[dreamx]

Originally posted by: jonnyGURU

Originally posted by: neptune
OK, so we got people saying combined, not combined and some other vaguaries.

That's the thing that sucks about going to forums for advice. Most of the advice is incorrect.

Originally posted by: neptune
The responses are appreciated, but can we get to a bottom line here; 2+2=4 kinda thing? So, if the GameXStream has 700W, 4 x 12V @ 18A each, will this combine to be enough for the purpose of this card? It will take all necessary juice that is required from the aggregate? How much does this PSU supply on the 12V rail overall? I will only be using the video card, and none of the other 3 connectors, so how much juice does the video get available to it? Thanks...

If you look on the sticker, right below where it shows all four 12V rails and their capability, there is a 12V combined rating:

http://www.jonnyguru.com/PSU/GameXStream700/IMG_0600.jpg

It's 680W (assuming no load on the 3.3V or 5V.)

So that means your combined 12V capability is 56.6A.

The GameXstream has a "rail" for each PCI-e. 12V3 goes to one and 12V4 goes to another. That means you have 18A available per video card. Full load I don't think each X1950 uses more than 10A.

When ATI suggests 30A, they're taking into consideration you're also going to need 12V for the CPU, drives, fans, etc. So the guestimate is "30A." But it's not that the card needs 30A or that all 30A needs to be on any single 12V rail.

nice info there for people like me who know nuts about PSUs

 

[kenji4life]

To add to what JohnnyGuru said (and listen to him he knows what he's talking about)
Many power supplies claim "4 rails" or "dual rails" but often times it really all leads down to the same circuitry. However in many other cases there are actual, physically separate rails as claimed.. as each PSU is different, this mucks up the whole thing completely. You really must go to a trusted site such as JG's or a site like silentpcreview.com, xbitlabs, tomzhardware or of course here at anandtech to see a review for your specific power supply. (this obviously goes to help anyone who would ask this question in the future about their specific power supply.)

 

[imported_neptune]

All right, now I feel better. Thanks for the info guys, and all without belittling anyone. How about that? Thanks again.