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GTX 560 Ti - Help understanding power requirements

Last response: in Graphics & Displays
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June 29, 2011 10:22:36 PM

Hi,

I've just purchased an eVGA GeForce GTX 560 Ti. I'm going to use it in a new computer but want to re-use my current PSU which is a Thermaltake W0106RU 700W. According to the specs for a GTX 560 Ti, it requires at least 30 amps on the 12 volt rail. The specs for my PSU are as follows:

Output: +3.3@30A,+5V@28A,+12V1@18A,+12V2@18A,+12V3@18A,+12V4@18A,-12V@0.8A,+5VSB@3.0A

I really have no idea what most of that means. However, I'm assuming that +12V(x) is the specs for the 12 volt rail. I see there are 4 of them with 18A each, so does that mean I have 72A on the 12 volt rail, or does it matter that they are listed separately and I'll need a different PSU?

And, for future expansion thoughts, if I have 72A on the 12 volt rail, does that mean I would be able to SLI dual 560 Ti without upgrading the PSU? The potential problem here is that I only have 2 6-pin PCI-E connectors, so maybe I'd have to get a newer one regardless?

I appreciate any help you can offer. Thanks.

Warren
June 29, 2011 10:27:30 PM

You can draw up to 18 amps per rail and up to 72 amps total from the 12V. The 560 Ti needs 170W at max load while your PSU can provide up to 216W per rail. Connect each 560 to a different rail or divide two rails for both of them (with each rail connecting to both cards).
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June 29, 2011 10:39:15 PM

OK. So, it seems I won't have any trouble running the one card. However, I have no idea how to tell what rail is what. All I know is that I have 2 6-pin PCI-E connections and a bunch of other cables coming out of my PSU. Can I assume that each modular connection on the PSU is a single rail? Where's the best place to find out how to understand how the PSU works? I'm in no hurry as I don't want to go SLI until performance dictates I need to.

Thanks for the explanation.
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June 29, 2011 11:38:23 PM

browsingtheworld said:
You can draw up to 18 amps per rail and up to 72 amps total from the 12V. The 560 Ti needs 170W at max load while your PSU can provide up to 216W per rail. Connect each 560 to a different rail or divide two rails for both of them (with each rail connecting to both cards).


Incorrect, its still a 700W unit and on its label it says max dc output 700W, which is about 58.3A from its 12V rail(this would be a best case scenario) realistically, probably only about 55A can be pulled from its 12V rail, you cannot simply add up the rails as 72A from the 12V rails would be 864W which is wayyy more than you should ever get from a 700W unit. I have explained it previously in more detail here

Single 12V rail or multiple 12V rails? The eternal question answered


As for the question at hand, that unit has sufficient power between its rails to handle the card without issue. The listed power requirements are for the system as a whole which is distributed across all of the 12V rails, the graphics card gets 75W from the PCI-E slot itself so it only needs about 100W from the connected power cables which is significantly below your limit on a single rail. It will work just fine to power the 560 Ti with that PSU.
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June 29, 2011 11:44:01 PM

hunter315 said:
Incorrect, its still a 700W unit and on its label it says max dc output 700W, which is about 58.3A from its 12V rail(this would be a best case scenario) realistically, probably only about 55A can be pulled from its 12V rail, you cannot simply add up the rails as 72A from the 12V rails would be 864W which is wayyy more than you should ever get from a 700W unit. I have explained it previously in more detail here

Single 12V rail or multiple 12V rails? The eternal question answered


As for the question at hand, that unit has sufficient power between its rails to handle the card without issue. The listed power requirements are for the system as a whole which is distributed across all of the 12V rails, the graphics card gets 75W from the PCI-E slot itself so it only needs about 100W from the connected power cables which is significantly below your limit on a single rail. It will work just fine to power the 560 Ti with that PSU.

Yep my mistake. Probably 48-52 amps.
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June 30, 2011 12:57:00 AM

Best answer selected by wsmithjr.
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June 30, 2011 1:00:21 AM

Great to hear. Thanks to both for your help.
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