New Computer Help

[Tellos Athenaios]

Power supplies must be bought slightly more powerful than strictly required because of the fact that various components wear out a bit (rather: some of their components build up a charge and others deform due to heat expansion both of which dilute the performance which means that the actual power they can deliver will degrade over time).

How much "over budget" you should go depends on how much you will use the system for (i.e. 24x7 systems require more margins than the occasional check-my-e-mail variety; and gaming machines need more than the occasional check-my-e-mail variety because the average load will be higher, which means that there will be more `wear'). A good -non generic- power supply typically has a nice "80" badge stuck on top of it, which says it has better than 80% efficiency; excellent ones will push well beyond that (e.g. 97%) but they are fairly expensive (you pay a premium for the power efficiency).

There are numerous PSU (Power Supply Unit) calculators out there; one I like in particular is this one: http://web.aanet.com.au/~SnooP/psucalc.php

Compare that to various others (usually a manufacturer will have a -biased?- one on its site) and you should get a good idea of what you need.

EDIT: Note that a power supply that is but slightly too weak will usually result in a (very) unstable system. You may experience random crashes; components may not work at all; loss of data because the system powers off the harddisk due to power failures. On top of that you are trashing the PSU which means its life time will be much more limited as a result.

EDIT2: Note if you are putting together the equipment yourself you may want to consider a modular power supply. Reason being a non-modular supply looks like a box with a boat load of wires sticking out of it at the back, whereas a modular supply is a box with a boat load of sockets at the back and a bunch of cables. This means you will have the option to only connect those cables you actually need which is less confusing and makes for an easier time when you will eventually have to force/route the cables in a more tidy fashion. (Otherwise they will very likely obstruct air flow towards fans and heat sinks as well as cover other sockets on your mother board; none of which is desirable.)