Is it ok to run GPU from 2 different 12v rails

[Flanno]

A bit of a strange question this. My PSU has 4 rails dedicated for GPU's...say 12V5,6,7,8. And each gpu modular connector on my psu corresponds to 1 of said rails. Each of the 4 pci-e cables I have has a 6pin and 6+2pin on it. So when running a GTX480 for instance you only need 1 cable and therefore it would seem you just use 1 rail.

Now here is my question. I've just bought a silverstone PP04 short cable adaptor kit to make things neater. It also comes supplied with 4 pci-e cables. Each one only has a 6+2pin connector. So to power a GTX480, I would need to use 2 cables. For instance, I would plug the 6+2pin into the modular connector on the PSU for 12V5, and the 6pin cable into 12V6. Is it safe to spread the load for a single GPU across 2 rails. I would obviously be doing the same for the 2nd gpu.

Also, I was looking at the NZXT individually prepbraided pci-e cables too. The NZXT 8pin cable is in fact just a 6pin male extension to 6+2pin female convertor. I was hoping it was a 6+2pin male to 6+2pin female. So I was wondering if it safe to plug the 6pin male end of this NZXT cable into the 6pin female end of the PSU's 6+2pin cable and just ignore the +2 part and hope it all comes out ok on the other 6+2pin end which plugs into the gpu. So 6+2pin psu cable ---> 6pin NZXT extension ---> converted to 6+2pin NZXT plugged into gpu.

 

[mmj_uk]

Yes infact I would say it was best practice to try to spread the load rather than putting too much load on a single rail.

 

[ubersonic]

Yes infact I would say it was best practice to try to spread the load rather than putting too much load on a single rail.

this

 

[Flanno]

Thanks. I think I read on jonnyguru the strider will join rails anyway if it needs more power. However it's good to know spreading the load purposefully accorss 4 rails won't cause any issues.

 

[drunkenmaster]

No, you should not spread a SINGLE device across multiple rails, because each of the rails can run at different voltages, IE 12.04v and 11.98v, thats the reasoning behind NOT using a single device on different rails.

I also wouldn't be certain of using propiatary cables for a specific PSU as they are often not compatible, sometimes because the connector is a different pinout on the PSU connection side(so you can't plug wrong connectors in to the wrong plug) and sometimes because the internal wiring will make it easier/make more sense to have a different output and then the wires hidden under braiding could actually be connecting to different pins on the other end.

So stick with connectors designed for your psu only, or make your own(I'm considering this as all my sata power connectors are miles apart yet my hard drives only about an inch apart so I've got lots of cable bent all over the place to attach all the drives, i've seen others make a run of sata power connectors with very little cable between them so they fit nice and neatly).

I'd fire off an e-mail to Silverstone to ask about the PSU if you really want to use your new cable, it will depend on the PSU, some just say they have more rails than they really do because some people like the sound of multiple rails, it may/may not have them.

 

[mmj_uk]

Most electrical devices have a +/- 5-10% tolerance so 0.06V difference isn't going to have any effect, putting too much load on a single rail will though if it can't supply enough.

 

[Flanno]

Thanks for the replies. I also asked over on Jonnyguru and it turns out the Stider 1500w had one big ass 12v rail in reality. So it doesn't matter much what I do. Silverstone claim the short extension cables I bought fit any strider series. Which is what I expected.

 

[jigger]

One single large rail is the best setup IMO.

 

[nayenshah]

Yes infact I would say it was best practice to try to spread the load rather than putting too much load on a single rail.

+2 on that! it makes perfect sense to modularise everything.