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Quick PSU Q's

V

vsboxerboy

2[H]4U
Joined
Oct 17, 2005
Messages
3,661
1. What do you call the extension that comes from the power supply that terminates in one or more connectors? you know what I'm talking about like an arm or something?

2. I have a power supply which I am not using two of the arms for and they really just get in the way. I am anal about my wires and want them to go away. Can I open up the psu, cut the wires within the housing and cap them so that they do not touch themselves, other wires, any metal, etc.
Is that cool?

3. I hear about rails when people talk about PSU's but don't know what that really means. Can each arm (or whatever you call #1) only support a certain amount of power? Ie is the power of the psu distributed equally among the arms or can a majority of the power go to one arm if I put a bunch of shit on it? I wanted to know this becasue I would be installing a 2x molex to 6pin PCIe connector to feed a new vid card but that arm also powers my optical drive and a few fans.
not that I am doing this, but what if I hooked everything in my system on one arm through the use of splitters or whaever. This is obviously the extreme situation but gets at what I'm trying to ask.

Thanks!
 
1.)You mean rails? That's how the power supply is divided up. The main ones are +3.3V, +5V, and +12V (and sometimes, multiple +12V rails), but they do not directly correlate to the number of connections a power supply has.

2.)You could, but if you need them later, then you're looking at a soldering job. If nothing else, this will void your warranty. If you want to remove cabling you don't use, you're better off purchasing a modular power supply.

3.)With the understanding of #1, each rail is specified for a number of amperes, or amps for short. If you overload the rail, the power supply may shut down.
By multiplying the amps by the voltage rail, you end up with the wattage for that rail.

Modern PSU's have a high-amp single +12V rail or multiple +12V rails, to address the issue of drawing more on a rail than it can produce. Your PSU is either going to have one large pool for everything on a particular voltage, or it's going to have it split up and fenced off.
 
wait, I'm not sure we are on the same page here. From my understanding, each arm that comes out of the PSU doens't have different voltages. I am defining the "arm" as the four (or more) wires that are grouped together which terminate most often in molex or sata connectors.

Are you saying that if you took two molex connectors from different arms they would have different voltages? no, right? Sorry I'm so confused on this lol. Here, what I am saying is that on a modular power supply, each of those modular connections, say you attach one that has SATA connectors, what do you call that group of wires?
 
I see.

The "arms" are just the wiring, that are not tied to the voltages and are not the rails. The +5V, +3.3V, and +12V I said are true, though. I was under the impression you thought something else, but I guess not. The rails are determined by the way the power supply is designed. There is a key, but it's the color of each individual wire. For the 4-wire cabling for SATA and molex, black is ground, yellow is +12V and red is +5V. I believe that applies to the ATX connector as well, but I'm not sure what the other colors represent. +3.3V, and if present, negative 5V, 3.3V, and 12Vs are probably represented, but don't quote me on that.

AFAIK, the modular "arms" are just referred to as cables. Some modular power supplies may have specific plugs for PCIe or SATA, but that's not universally true. They seem to be employed to keep people from plugging things in that shouldn't be or to make use of multiple +12V rails.
 
Certain PSUs have 2 x 12V rails. Are they better than the ones with just one full 12V rail and also why?
 
No, multi rails aren't necessarily better than single rail PSUs. Multiple rails were put into mass use when the ATX spec only called for a max of like 20A on the 12v rail so when the companies needed to supply more, they just broke up the amps across different 'rails'. A strong single rail PSU can often times be better than a multi-rail as for the most part, you'll be looknging at a PC power and cooling psu, which are top notch and nearly the only single rail psus in existence anymore. People argue back and forth which is better, it doesn't really make too much of a difference for the average user.
 
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