GTX 480 SLI Question

[rolodomo]

I can get a used 480 cheap as a second card for SLI.

I'm thinking about buying a dedicated PSU for this second 480 ONLY. My case has plenty of room for a second PSU. That way, when I don't need SLI (which will be common), I just keep the second PSU off and the second 480 drops out of the picture completely (consumes no watts and generates no heat).

Plus, no need to chuck my existing Seasonic 850W M12D. I'll just buy a good quality (and fairly cheap) second PSU (approx. 500W or so).

Is this actually a bad idea? I don't think I'll get any loop currents between the PSU(s), but I'm just not sure the computer will boot (safely?) with a second, unpowered graphics card sitting in a PCI slot. Anyone ever tried it or have any suggestions otherwise? Thanks!

 

[pugh]

Sounds like a disaster waiting to happen. If I were you I would get myself a quality 950w -1kw psu and call it a day. If you are wanting to run dual gtx480 why not do it the right and sound way?

From what you said SLi not being a common thing. Why go that route then? GTX 480 not handling the games you play?

 

[rolodomo]

Sounds like a disaster waiting to happen. If I were you I would get myself a quality 950w -1kw psu and call it a day. If you are wanting to run dual gtx480 why not do it the right and sound way?

From what you said SLi not being a common thing. Why go that route then? GTX 480 not handling the games you play?

I liked the idea of getting one of the cards to disappear completely (power and heat wise) from my system when I don't need SLI. But yeah, I'm not finding anyone who has actually done this config via Google, so that's probably not a good sign. Thanks for the feedback.

I was thinking about using SLI for 3D gaming and future-proofing about a year out. When I'm browsing the net though, the thought of a second GTX 480 sucking down 150 W (even while downclocked and idling) really bothers me.

 

[nenforcer]

I'm in the same boat, I've got 2 X 9800GT in SLI and its just too much heat and power just to surf the web.

This is why I mainly still use the rig in my sig for such things.

How would you do it, do you turn on the secondary power supply first before powering on the main power supply, or vice versa?

Then when you are turning off the computer to only use one video card do you just shutdown the machine and then power off both supples and then finally power back on the main supply?

I've never heard of this being done and never seen a case that could accomodate 2 power supplies. What case are you using?

 

[rolodomo]

How would you do it, do you turn on the secondary power supply first before powering on the main power supply, or vice versa?

Then when you are turning off the computer to only use one video card do you just shutdown the machine and then power off both supples and then finally power back on the main supply?

I've never heard of this being done and never seen a case that could accomodate 2 power supplies. What case are you using?

My normal mode would be single GPU, so the secondary power supply (which feeds the second 480 only) would be switched off.

If I wanted to change to SLI mode, I would turn off the computer, turn on the switch to the secondary power supply, then boot. Windows 7 should boot with the NVIDIA drivers seeing both 480(s). I then go into the NVIDIA control panel and select SLI.

If I wanted to change back to normal mode, I would go into the NVIDIA control panel and turn SLI off. I would then turn off the computer, turn off the switch to the secondary power supply, then boot. Windows 7 should boot with the NVIDIA drivers only seeing the first 480.

Unless it blows up. 😉

My HAF 932 case has a bottom-mount and top-mount option for the PSU, so I could easily add a second PSU to the top-mount.

 

[pugh]

If I wanted to change to SLI mode, I would turn off the computer, turn on the switch to the secondary power supply, then boot. Windows 7 should boot with the NVIDIA drivers seeing both 480(s). I then go into the NVIDIA control panel and select SLI.

If I wanted to change back to normal mode, I would go into the NVIDIA control panel and turn SLI off. I would then turn off the computer, turn off the switch to the secondary power supply, then boot. Windows 7 should boot with the NVIDIA drivers only seeing the first 480.

This was along the lines I was thinking would be a safer route. You are already running a powerful card. You will have to come too some decisions on which route you want to take I guess.

 

[Qbah]

I don't think that's a good idea. The card also sips power through the PCI-e slot, not only through the PCI-e 6/8-pin plugs. Since it's not coming through the same source, I can imagine lots of nasty things happening to the card. It would work if you link both PSUs to power the motherboard (that's how specialized additional PSUs work - it makes both of them a common source) but then you can't really power them up/down separately (both controlled by the chassis power switch). Hence you're still in the same place - either both are on (and both cards are powered up) or the computer is off 😛

 

[BTRY B 529th FA BN]

Your 850w is more than enough. Unless you just want to strictly run Furmark ONLY.

First, buy yourself one of these or something similar:

http://www.newegg.com/Product/Produc...-001-_-Product

They also have something similar at Lowes & Home Depot. Here is the one I use:

click to enlarge.

That is my 3rd rig in sig running Unreal Tournament III. The machine also idles @ 144w but get one of these ~20$ items first before you go buying another PSU 🙂

 

[solofly]

Sounds like a disaster waiting to happen. If I were you I would get myself a quality 950w -1kw psu and call it a day. ?

Yep u cut corners and u'll pay in the long run...

 

[rolodomo]

I don't think that's a good idea. The card also sips power through the PCI-e slot, not only through the PCI-e 6/8-pin plugs. Since it's not coming through the same source, I can imagine lots of nasty things happening to the card. It would work if you link both PSUs to power the motherboard (that's how specialized additional PSUs work - it makes both of them a common source) but then you can't really power them up/down separately (both controlled by the chassis power switch). Hence you're still in the same place - either both are on (and both cards are powered up) or the computer is off 😛

Yes, good points. I forgot about those addon PSU(s) you add into a vacant drive bay. Too bad they defeat my purpose (as you indicated).

 

[rolodomo]

Your 850w is more than enough. Unless you just want to strictly run Furmark ONLY.

First, buy yourself one of these or something similar:

Thanks for the links, I've been meaning to pick one of those up. I'll check power consumption before buying a new PSU. I don't plan to overclock that much in SLI mode, so perhaps I'll have a figting chance with my 850W PSU.

 

[rolodomo]

Yep u cut corners and u'll pay in the long run...

I know, but it is a form of tweaking. Yes, I wanted to save money on the PSU, but it also would have been a very efficient solution. Hoping someone would respond, "yes, been doing that for years, works great because...." I appeciate the warnings however, so I'm not going to try it.

I will try to see if I can lean on my Seasonic 850W. According to the reviews, it maintains rated efficiency at top-end loads.

 

[Spikesoldier]

bad idea. i would stay away from the second PSU. also, i dont think that you can shut power down to the second card and expect it to work in SLI immediately after flipping the switch.

for the two 480s i would begin to worry whether 850w is enough but since you have a good quality unit, i would trust the SLI'd system to the seasonic.