Test cases

A Straightforward Example

Antec makes great power supplies, so let’s look at them. The ~$50 Antec 350W (SL350) power supply has

28A on +3.3V
35A on +5V
16A on +12V

Based upon these specifications, the Antec offers more than the minimum spec, and so in most cases the system will be very good. It’s not the “80% of efficiency” that we’d prefer, but it should be all right.

The Antec SL350 power supply

Note the power figures on the power supply

A Tricky One

What about a 265W Enermax EG265P-VE?

22A on +3.3V
25A on +5V
18A on +12V

This offers plenty of power on all three rails, and in fact it’s even better for the +12V rail, but remember, we need 279W at peak use. Here, our peak is 265W. Not enough. The 300W Enermax has the following spec:

28A on +3.3V
30A on +5V
22A on +12V

Now, the individual rails are good enough for us and the total wattage is sufficient for our minimum. If you didn’t want the extra piece of mind at running 80% maximum efficiency, the Enermax seems to be a good choice. If you wanted the extra piece of mind, the 350W Enermax will give you top-notch performance.

Generic Power Supplies

That said, most of us don’t buy power supplies independently. We get case/powersupply combos – I mean, why spend $50 on a power supply when you can get a case+power supply for $50? Let us take a look at the Foxconn Mid-Tower with “AMD Listed 300W power supply” that a store like newegg has for $30.

20A on +3.3V
30A on +5V
10A on +12V

The 3.3V and 5V rails are great, but the 12V rail is too weak for our system! Under heavy processor load, Athlon XP system would be very unstable and likely spontaneously reboot. What about another 300W power supply such as the Codegen for $30?

20A on +3.3V
25A on +5V
10A on +12V

Still not enough. Let’s go up to 350W generic cases. $38 gets you a nice looking Foxconn setup with “350W AMD recommended power supply up to XP2100+”


24A on +3.3V
35A on +5V
12A on +12V

Better, but the 12A still isn’t enough for our system since we have too many drives. What about a $56 400W generic case?

24A on +3.3V
35A on +5V
12A on +12V

What the heck? A 400W and 350W power supply offer the exact same specs? Well no, the individual “power pumps” for the +3.3V and +5V and +12V are the same, but the pump at the power source is bigger.

What about a generic 450W power supply?

By now, you might think that “buying a generic case is just a bad idea.” In that case, lets look at Newegg’s $68 Chieftec with a 450W “AMD approved” Austin power supply.

28A +3.3V
30A +5V
15A +12V

The +12V is just good enough to meet your bare minimum spec, but don’t think about adding extra hard drives. This power supply is capable of providing a lot of juice to the +3.3V and +5V rails, but you really have nothing useful there. It’s the 12V you’re worried about and this 450W only provides a maximum of 180W on +12V.