Articles :: Modular Power Supplies: The Reality of the Resistance. :: Motherboards.org
Jon Gerow · 08-10-2006 · Category:
Hopefully you all found
my little experiment entertaining and informative, if not monotonous and
overly in depth. Obviously, it's fighting a losing battle trying to convince
anyone that modular
don't create any significant resistance, but I think there's a few things here
we can all learn from.
Someone once said that
a modular connector's pins have as much resistance as two feet of wire. I
can't recall where that came from, but I think our five
subjects have shown us that there's actually as much as four times as much
voltage lost in a mere 18 inches of cable than there is in a modular connector.
And when thinking about a loss in voltage in a modular connector, one shouldn't
look just at the fact that a power supply has a modular connector, but perhaps
how that modular connector is made.
The power supply that showed
the most drop in voltage at the modular connector was the Corsair. I'm not
really sure why this was since the connector was a one to one with a standard
6-pin PCI-e type connector. I could understand seeing this kind of drop with
the other modular connectors on the Corsair because relatively
small pins are used in the five pin connectors that
into the power supply housing. Below is a close up picture of one of the
Corsair modular peripheral power connectors.
Regardless of why there
was this drop when the Corsair was under load, one has to keep in mind
that this drop was only .03V even when there was an 11A
That's only a 0.25% drop in voltage during a very exaggerated static
The power supply that showed
the most drop in voltage through the cable was the Antec. This probably has nothing
to do with the gage and length of the wire, but because there are four conductors
splitting off into six wires. Two of these wires meet into one contact,
twice the resistance as the other conductor. Below is a close up of the back
of the Antec connector...
Note how only four of the potential six pins are used. If you take a look
at the photo below, you can see why. The connector on the right is the one
used for PCI express. The one on the left is used for a four pin peripheral
power connector. The 12V lead in the lower right is missing, but now there
is a 5V in the upper right that the PCI express connector did not have. The
upper left would house a 3.3V conductor for use with SATA drives.
Again, we have to admit
that the drop was only .19V, even with an 11A load, as opposed to the .11V
drop we saw on
Silverstone power supply's cable which had no modular connectors at all.
Now please keep in mind
that this article is in no way a power supply review. You have not just witnessed
some sort of weird five-way power supply shootout. There are so many good
things to say about ALL of the power supplies I used today. For example,
the voltage drop going from 0A to 11A on both the Antec NeoHE and Corsair
HX620W was actually LESS than the FSP600-80GLC power
supply with fixed cables. But the focus
of today's article was to simply clarify some of the fuzzy math used to create
fud over modular power supplies, therefore we focused primarily on the drop
from the power supply's PCB to the load.
Of course, despite today's
findings, we still can't ignore some KNOWN ISSUES with modular power supplies
that we all need to be mindful of. Any physical connection point, whether
you're talking about the modular connector on a power supply or a lug nut
on your car's wheel, is a potential point of failure. Connections can work
loose. But in some applications they don't work loose once they are in place
because, unlike your car's wheel, your power supply is not a moving
I have seen people assemble builds with modular power supplies, tie things
up all neat and tidy, and then NOT go back to double check the security of
the modular connections at the power supply. This can, and DOES, cause HUGE
check ALL of your connections whenever you open your case, shove your hands
inside and start bumping and yanking on different cables.
And if you're the
type of person that moves their stuff around inside their case, or even
moves their stuff from case to case, be aware that by repeatedly plugging
your cables you may be working them loose. A loose cable is going to have
more resistance than a nice firm one. If you feel your cable is working
loose throw it away and replace it!
- Testing Methodology / Testing Corsair HX620W
- Testing Corsair HX620W (continued)
- Testing Corsair HX620W (results)
- Testing Ultra X2 550W
- Testing Antec NeoHE 430W
- Testing Fortron Source FSP600-80GLC
- Testing Silverstone ST65ZF
- Charting voltage output results for all five load tests
- Side by side comparison charts of voltage output