Power supply question

[DaTT]

Say i get a graphics card that requires a +12v rail to have 30A, and my current PSU has 4 +12v rails at 18A each....what exactly does that mean? Do they stack? This was an expensive PSU and I would like to continue using it. Claims it is SLI ready, I'm a little worried about this.

I really don't understand what the rails are.

Thanks for your help

 

[lehtv]

Should be in Power Supply forum.

Each of the four rails can provide up to 18A individually, but the total combined output will be slightly less when divided by 4. For your PSU the combined +12v load is 768W, or 192W per rail, or 192W/12V = 16A per rail. Also, more info on rails here.

Which GPUs are you planning to SLI?

 

[DaTT]

Should be in Power Supply forum.

Each of the four rails can provide up to 18A individually, but the total combined output will be slightly less when divided by 4. For your PSU the combined +12v load is 768W, or 192W per rail, or 192W/12V = 16A per rail. Also, more info on rails here.

Which GPUs are you planning to SLI?

Was not aware there was such a forum until just now. Mods please move thread as I will be continuing to use this one.

Anyways, I don't plan to SLI anything...just the card I was looking at says it requires a +12v rail with 30A. I am hoping this PSU will work just fine, and that is basically what I am asking. I only brought up the SLI stat because I figured that would require more amps, it was just thrown in as reference I guess.

 

[lehtv]

Which card is that?

 

[DaTT]

I am still thinking about the GTX 560 Ti

I just noticed that it requires 2 6 pin +12v, now would that be 36A due to it having 2 18A inputs?

 

[lehtv]

I'd expect two of the +12V rails to power two PCIe connectors each, with one of the remaining two rails powering the CPU, and the other one powering molex connectors etc minor +12V components. So in a SLI setup you'd be powering two 560 Ti's from two rails. It should work fine, since a 560 Ti at stock requires about 170W and the rail maxes out at 18A = 216W. Not 100% sure whether overclocking the GPUs would be a good idea.

On another note, I'd recommend against 560 Ti SLI, it's better to SLI/crossfire cards with more than 1GB VRAM.

 

[DaTT]

I'd expect two of the +12V rails to power two PCIe connectors each, with one of the remaining two rails powering the CPU, and the other one powering molex connectors etc minor +12V components. So in a SLI setup you'd be powering two 560 Ti's from two rails. It should work fine, since a 560 Ti at stock requires about 170W and the rail maxes out at 18A = 216W. Not 100% sure whether overclocking the GPUs would be a good idea.

On another note, I'd recommend against 560 Ti SLI, it's better to SLI/crossfire cards with more than 1GB VRAM.

I am not powering 2 560's. Just one. I only mentioned SLI because the PSU said SLI ready.

1 GTX560Ti requires 2 6-pin +12v inputs.

 

[lehtv]

With one 560 Ti, you'll divide the power of one GPU between two rails as long as you use PCIe connectors from different cables (assuming it has two cables with two connectors each; if it has four separate cables, you may not have a way of knowing which cables go to which rails). Obviously that won't load the rails anywhere near their maximum

FYI the "minimum 30A" recommendation (whereever you got that from) applies to the total +12V output of the PSU

 

[DaTT]

Excellent. Thanks for your help again.