Single vs. Multiple +12V rails: The splitting of the +12V rail

[jonnyGURU]

Originally Posted by spursindonesia

If the system uses a PCI controller or two, that scenario might very well be true, right ?

Yes. But the controller's not going to be on the motherboard. That's what I was saying. I would hope that if you had 10 HDD's on a computer you would have staggered start up regardless of what kind of PSU you had.

[rip97000]

jonnyGURU:

i recently saw a couple power supplies that could "switch" (auto and manual) between multiple 12v and a single 12v rail. would this also be a marketing gimic?

On Tagan’s website they mention a “Turbo Mode” to which all six rails can auto-magically be converted into a single beady 12v rail.3dgameman.com

Manual +12V rails “TURBO” mode can integrate +12V rails into single rail with more DC output for heavy +12V loading. technoyard.com

[HOOfan_1]

I am wondering if that just turns off the Over Current Protection or something.

[cypherpunks]

Originally Posted by rip97000

i recently saw a couple power supplies that could "switch" (auto and manual) between multiple 12v and a single 12v rail. would this also be a marketing gimic?

Well, once you understand that "multiple rails" is only about current limits, it should be blindingly obvious what that "feature" does: ignores the current limits. I've seen these "automatic rail fusion" lights, and that's simply connecting the overcurrent detector to an LED rather than shutdown.

So it depends on what you define as a "gimmick". It is something that the PSU does differently, and not just a fancy name for a feature that all PSUs have. But it is just a fancy name for a simple feature, and further misleads the people who think that the power the electric company provides to them is somehow different from the power it supplies to their neighbour.

[rip97000]

cypherpunks:
forgive me i have horrible spelling (gimic vs gimmick above)

i understand current limits and multiple rails, but i was asking more about what jonnyGURU said above (sorry i'm not good at these forums and explaining what i mean yet):

Is it true that some PSU's that claim to be multiple +12V rails don't have the +12V rail split at all?

Yes, this is true. But it's the exception and not the norm. It's typically seen in Seasonic built units (like the Corsair HX and Antec True Power Trio.) It's actually cheaper to make a single +12V rail PSU because you forego all of the components used in splitting up and limiting each rail and this may be one reason some OEM's will not split the rails, but say they are split. Some system builders adhere very closely to ATX12V specification for liability reasons, so a company that wants to get that business but also save money and reduce R&D costs will often "fib" and say the PSU has it's +12V split when it does not.

so are companies "fibbing" when they claim to switch between single and multiple rails?

[HOOfan_1]

Originally Posted by rip97000

so are companies "fibbing" when they claim to switch between single and multiple rails?

looking at Jonny's review of the NZXT (built by Topower) I would say yes....looks like this PSU doesn't use OCP whether the switch is on multi or single

[Makalu]

Good work Jon...something about the "multiple rails trap power" FUD would be nice to see too.

[Killy]

So, in the end, a well done multi-rail psu > single rail?

[Stefan555]

I would say a well done multi-rail = single rail, no differences apart from rail distribution and safety

[Smirnoff]

Very enlightening, and bookmarked for later reference. I was one of those who fell for the "single rail good, multi rail bad" thing.