My aging workstation's PSU is giving out after 5 years of 24/7 service. It had a 38 amp 12v rail that just isn't cutting it with its age and the additional hardware it's running. I think the 550w peak output is still OK but the 12v is getting shaky. I think it has taken the form of completely random reboots when playing games or video (the new card is a power hog I think). So to salvage this rig for the now I'm going to replace the PSU but I'm wondering what the difference is between a solid single 12v rail and a PSU with multiple 12v rails. I'm looking at two different PSUs, one has three 12v rails at 19 amps and the other has a single 60 amp rail. I'm guessing multiple rails is good for multiple video cards as you can dedicate one per card, one to the mobo, and another for peripherals? However what's wrong with one massive 12v rail? Things to keep in mind with this decision: This PSU will likely migrate to the new rig, a dual-quad built around the Penryn-based Xeons in a few months. It probably won't be SLi because I think the idea silly and I don't game enough for it to be worth the cost. This PSU will drive both the hungry quads, 4-8GB of memory, a single mid-range video card, and a ton of HDD space in various flavors (7200rpm SATA, 10krpm SATA, 15krpm SCSI/SAS). BTW I'm leaning toward the PC Power & Cooling 750W. I've heard only good things about their PSUs and have always wanted to integrate one into one of my SMP systems. I imagine the reliability and build quality is just fine with the single 60 amp 12v rail.
PC P&C has always been solid, personally I run a Corsair HX620 which has been fine for my rig (e6550, 2gb ram, 3 hdds, 8800gts). http://www.jonnyguru.com/ is pretty much the place to go for psu reviews, though.
Quality power supplies are the way to go. I have had good luck with the Enermax supplies in the past and they are in both my current machines. I know PC Power and Cooling have a solid rep and always rated towards the top in any ps shoot out. Only downside (besides being pricey)is they are a bit loud from what I have read. They claim having a single rail is the way to go due to power loss with multiple rails. http://www.pcpower.com/technology/myths/ An alternative is multiple power supplies, the recent CPU mag has an article on doing that. That way you can dedicate a power supply to drives or the video card(s) since they can be a 12v hogs. Depending on the number of drives that 750w may not be big enough. I don't think you can go wrong with that choice.
Multiple rails are really just hype due to the way the are implemented... Go with a good name supply and you will minimize any issues. PC is a good choice. Christian
