Resolved (dis)advantages of using multiple PSU rails

I realize the SSD, HDD and DVD-ROM can be run off of one rail (for cable management), but would there be any advantage to using dedicated rails? The 3 don't come close to the rating of the rail, but I'd hate for anything to burn out because another component shorted or have the start-up of one component impact the start-up of another.

Details:

Antec HCG M 850W 80+ Bronze Certified Semi-Modular ATX Power Supply (40A/rail)

Crucial M550 256GB SSD (0.15w)

Seagate Barracuda Desktop 6-Gb/s 1TB Hard Drive ST1000DM003 (6.19w)

Generic DVD-ROM (IDE - SATA adapter used) (1.8A)

 

Separate rails for computer PSUs was a marketing gimmick from a few years ago that fizzled out for many reasons.

Multi-rail PSUs were commonly used years ago in analog communications systems to help avoid interference (noise) from entering adjacent channels. They were also commonly used for redundancy purposes on "mission critical" systems. But digital technologies and better isolation techniques changed all that - at least on the interference side.

Multi-rail PSUs require a more complex design to isolate the rails from each other using more parts. Therefore, they tend to cost more and have more potential points of failure. Multi-rail PSUs must keep a reserve of power on every rail, even when it is not in use. This then requires the use of a bigger and more expensive PSU to ensure there is enough oomph on each rail. This means a potentially significant percentage of the PSU's power may go unused.

Single rail systems are less complex, with fewer parts so are less prone to failure. And, if properly sized, ensures there is enough power for all connected devices. For this reason, most PSUs today are single rail.

Just to ensure there is no confusion here, separate cables don't mean separate rails. In today's PSUs, the +12V voltage, regardless the cable coming from the PSU, all feed off the same rail inside the PSU. And there is nothing wrong with that.

 

Based on what you're saying, I sense you're telling me I might as well run all 3 components on one cable, as running multiple cables won't change anything. That is what we did, but we were open to running multiple cables if it might be advantageous in any way.

 

Exactly! As long as you have enough connectors on the cable, you can keep adding devices. In this way, you can remove the unused cables (if a modular supply) or tuck the unused cables out of the way if hardwired. This is good "cable management" as it limits the restrictions excess cables put on the desired air flowing through the case. It also presents a tidier, more professional appearance.

 

Thank you. I'll put a picture along with all the components on this build, once everything is complete (on my original post). We're still waiting on Crucial to ship the RAM.