Dual power supplies and 'crossloading' concerns

[Rock&Roll]

So I'm making considerations for some system changes involving GTX480 in SLI using the system in my sig. The situation may require me to go to dual-ed power supplies (Actually, only if I decide to add an 8800 card for physX)

The problem I've read about is that 'crossloading' a power supply is a bad thing....that not having a load on the 5v and 3.3v is a problem.

So far, my searches for further information beyond that hasn't turned up much. The obvious answer is to put a dummy load on the 5v and 3.3v rails. However, I'm not 100% sure it's even necessary.

Would it cause harm to a PSU to run in 24/7 (not just benching) with only the 12v rails being loaded?

 

[Tolyngee]

While you don't mention what PSU you're intending to use, but I've used my 750TX Corsairs as dedicated hard drive PSUs and dedicated GPU PSUs before without any problems. I just use these to turn 'em on:

http://www.servercase.com/Merchant2...duct_Code=ATX-to-AT+cable&Category_Code=Acce.

 

[CanesVenetici]

Bad link

 

[davidhammock200]

Add a "GPU Booster" PSU, it fits in the 5.25" bay.

What PSU are you using now?

 

[Elledan]

Modern PSUs are generally fine with most and sometimes all of the load on 12V. Look for PSUs using VRMs to generate the minor voltages; these are basically 12V PSUs with separate modules for the other voltages and don't care about cross-loading on 12V-only much if at all. Good PSU reviews will have the cross-loading tests included and should give you the answer you're looking for.

 

[Rock&Roll]

Thx for the replies guys.

HX1000. By my calculations, I stay under the 40A rail limit with just the system and dual 480's. Adding the 8800 on either rail puts me over the top on one of the rails.

I'm basing this off of the PSU calculator at 90% system load http://extreme.outervision.com/psucalculatorlite.jsp

I've heard that if you balance an HX1000 right, you can get 1100+ out of it. However, I don't like the idea of running a PSU so close to the limit. I have a Silencer 750w I could dual up with.

I know about the dedicated VGA PSU's. As of now, that's not an option.

 

[Rock&Roll]

Here's my initial numbers:

12V1
system 	288w @90%
PhysX  	125w @90%
Total:	34.4A @90%

12V2
Pump & drives 	90w
GTX480(1)	215w @90%
GTX480(2)	215w @90%
Total:		43.3A @90%

Alternate

12V1
system 		288w @90%
GTX480(1)	215w @90%
Total:		41.8A @90%

12V2
Pump & drives 	90w
PhysX  		125w @90%
GTX480(2)	215w @90%
Total:		35.8A @90%