-=PCTechTalk=- Re: Power Supply
- From: Gman <gman.pctt@xxxxxxxxx>
- To: <pctechtalk@xxxxxxxxxxxxx>
- Date: Fri, 13 Jun 2008 18:57:06 -0400
Just seeing you asking this question has me smiling from ear to ear. It
means you're really pouring some intense interest into this stuff. My
answer is "Yes, but ..." since there are advantages & disadvantages to every
type of choice like this. :O)
Before I launch into a more in-depth description of rail setups, I have to
make it clear that devices are rated by what they normally draw from a PS
"during use". They are often capable of drawing more than that amount if
they are being stressed. This stress occurs when you fire up your system
and power is simultaneously sent to every device at once as well as when
individual devices are run beyond their normal operating parameters such as
when you are working with video or 3D rendering, playing most modern major
gaming titles with lots of graphics options enabled, etc.. However, many
devices just sit there sipping tiny amounts of juice until they are actually
called into duty. Any optical drive would be a perfect example since they
do nothing until you actually put in a disk and do something with it.
Therefore, it's not just the rating of the device that needs to be tallied.
You also need to consider how often it's used as well as what other devices
are likely to be in use at the same time. Finally, the ones I'm discussing
are limited to the rails that supply 12 volt power to major peripherals such
as the mainboard, hard drives, optical drives, modern video cards, etc..
This discussion does not take into account the lines that supply other
voltages since those follow a single rail standard on every PS.
For power supply rail options, I'll start with the disadvantages. If a
single rail PS should fail, the entire unit is toast (but if you're handy
with electronics & soldering, you can usually repair them yourself). A
multi-rail setup breaks up the available power across more than one rail and
that means you will have what I refer to as 'slack' power. In other words,
if there are two rails and both are rated at 16 amps, you can approach 16
amps, but not go over without seriously stressing that part of the unit.
So, you might end up with 15.5 amps worth of devices relying on that rail.
That leaves 0.5 amps of this 'slack' power that's basically worthless to
your system (although it does provide a tiny bit of headroom if one of your
devices should ever need it). The other rail may have 10.5 amps worth of
devices connected to it, leaving 5.5 amps of slack. This rail has a much
more comfortable pad of headroom for use by any of the components powered by
that rail. On the other hand, a single rail setup would have all 6 amps of
slack ready to be used by ANY device anywhere on your system as the need
arises. No device would be starved for power unless you attach more devices
than the PS is rated to handle. To make matters worse for multi-rail
setups, someone not understanding this stuff could easily cause one of their
rails to fail prematurely by overloading it (exceeding the individual rail's
rating with devices that are often in use).
As for advantages, a single rail system ensures that nearly every drop of
power that is not used to power the PS is available equally to the
components in your system. On the other hand, a multiple rail arrangement
is more forgiving if one of the rails ever fails (you still get the use of
the other rails).
So yes, I sure do prefer single rail PS's for most things, but I also miss
the idea that a single rail blowout in a multi-rail PS can still leave me
with a usable PS with a lower overall rating (and less connectors, of
course). I will also note that I am currently running a multi-rail PS in my
main system, my preference having been negated by a really good deal on a
really good PS that happens to sport a two rail setup. Knowing what I've
learned about this stuff over the years let's me divvy up 'the juice' fairly
equally among the devices so I don't lack in headroom anywhere. lol
Peace,
G
"The only dumb questions are the ones that are never asked"
----- Original Message -----
From: "cajun12" <cajun12@xxxxxxx>
To: <pctechtalk@xxxxxxxxxxxxx>
Sent: Friday, June 13, 2008 4:44 PM
Subject: -=PCTechTalk=- Power Supply
> G-Man, are you a fan of Single Rail power supplies?
>
> dj
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