MODULAR PSU VS. NON MODULAR + SINGLE +12V rail vs. Multiple

[b-star]

Hi again,
how will you comment this topic:


DON'T LOSE POWER WITH MODULAR PLUGS

Due to their look, convenience, and cost savings for manufacturers, modular plugs have become a popular power supply feature. Unfortunately, there has been little or no discussion of the impact of this feature on overall performance and reliability. The fact is, modular plugs limit power by adding to electrical resistance. The voltage drop can be as much as would occur in 2 feet of standard wire. Worse yet, modular plugs utilize delicate pins that can easily loosen, corrode, and burn, creating the potential for a major system failure. That's why professional system builders specify uninterrupted wire!"



ARE MULTIPLE 12-VOLT RAILS BETTER THAN A SINGLE 12-VOLT RAIL?

With all the hype about multiple 12-volt rails (ads claim that two rails is better than one, five is better than four, etc.), you'd think it was a better design. Unfortunately, it's not!

Here are the facts: A large, single 12-volt rail (without a 240VA limit) can transfer 100% of the 12-volt output from the PSU to the computer, while a multi-rail 12-volt design has distribution losses of up to 30% of the power supply's rating. Those losses occur because power literally gets "trapped" on under-utilized rails. For example, if the 12-volt rail that powers the CPU is rated for 17 amps and the CPU only uses 7A, the remaining 10A is unusable, since it is isolated from the rest of the system.

Since the maximum current from any one 12-volt rail of a multiple-rail PSU is limited to 20 amps (240VA / 12 volts = 20 amps), PCs with high-performance components that draw over 20 amps from the same rail are subject to over-current shutdowns. With power requirements for multiple processors and graphics cards continuing to grow, the multiple-rail design, with its 240VA limit per rail, is basically obsolete.



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[lankymorley]

I've read a little about this in the past and I was quite concerned at first, but the reality of it is that although there may be minor voltage drops with modular, it's not significant enough to cause instability. The majority of power supplies from the big manufacturers will be more than reliable enough for even enthusiast systems.

 

[Kennysevenfold]

im not too fussed about modular or non modualr myself, i just take my time and keep things tidy

as for the rails, i do prefere a single 12v rail as i feel it is more stable, but to be honest do we really notice.?

 

[EsaT]

Stop reading that excrement of PC P&C's BS... PR department!
Already common sense should tell that modular cables are clear additional cost and not saving!
And only review about voltage losses in cabling of various PSUs had losses distributed entirely "randomly" regardless of modularity.


And there has never been really multiple 12V rail PSUs!
They're nothing more than artificial current limiters in wire groups: Same as fuses in houses.
And introduced for similar reason, some decided to limit highest current available from single wire to 20A for safety reasons in user installable devices which become problem when 12V output of PSUs rose over that. So they started dividing wires to these current limited groups but instead of telling the truth BS departments started spewing out that crap about better stability.
In normal situation those don't cause any problems and actually can be good for safety because of limiting current in failure/shortcircuit situation but PC components aren't "standard sized loads" but have widely varying power needs so it's possible to have situation when one wire group reaches current limit leading to shutdown of PSU much before actual 12V capacity is reached.
Apparently PC P&C itself was originally all for these current limitations but was then caught pants down with lousy distribution of cables/connectors to these limiters and then reversed course.

Only exception to lack of separate rails are Enermax Galaxys which have two groups of limiter behind separate transformers. And there's the situation where power gets trapped so that it can't be utilized: Entire half of 12V output is available only for CPU and motherboard when in PCs actually requiring that big PSU graphic cards would be responsible for three fourths or higher part of 12V power draw. (because of component size reasons many high power PSUs actually have two 12V transformers but their outputs are combined)


I'm myself against this virtual rail crap in general because it even makes it easier to hide bad specs of PSU: When Joe Average Vegetable... err Consumer looks PSU only thing he sees is number of these "rails" and often even summs them together which is always above real 12V output and way above that in crappy PSUs.
One of the reasons for me always recommending Seasonic made PSUs (besides consistent quality) is lack of these limiters. Seasonic has made PSUs to UL Level 6 class for years meaning they don't have that 240VA/20A limit requirement.
Their newest M12D models apparently have two real current limited wire groups but I don't have quarrel with that because limits are so high that it's extremely hard to load PSU such unevenly that this limit would be reached before full 12V output and simply because when maximum output rises much above 50A it becomes hard for anykind shortcircuit/overcurrent protection to react to faults because short circuit simply has to be very good to be able to draw enough current to trigger them!
If one wire shorted resistance of wire itself could limit current below triggering level of protection and PSU would continue heating wire burning hot until short circuit burns away or resistance drops enough.