AMD Athlon Buyer's Guide - Part 4: Power Supplies

Now that we’ve proven that the Athlon does in fact require a significant amount of power, what are some important things to look for in a power supply? 

The power supply’s main function is, obviously, to supply power to your system and it does that by first converting the Alternating Current (AC) it receives from your wall outlet to a more usable form to the computer known as Direct Current (DC).  As the name implies, Alternating Current provides an alternating signal while Direct Current provides a current that remains at a constant level.

After converting the current it receives from the wall outlet to DC, the power supply then supplies a set of voltages to your system, more specifically +5V, -5V, +12V, -12V, and +3.3V.  The ability of a power supply to properly deliver enough power on each one of these voltage rails is what we’ll be concentrating on in this comparison since the under delivery of power to a critical device can result in system instability which has been the case with many Athlon setups.

You’re used to hearing a power supply defined by a rating such as 250 Watts or 300 Watts (W), but there is much more to a power supply than whether it’s a 250W or 300W unit.  You’re going to want to know exactly what the power rating on each one of the voltages described above is, which provides much more information than simply knowing if you have a 300W unit or not. 

First of all, you’re probably not going to want to pay much attention to the –5V and –12V ratings on a power supply since they aren’t of much importance to driving the components in your system. 

To AMD, the rating on the +5V and +3.3V rails is the most important because those are the voltages supplied to the motherboard and the CPU.  The combined rating, as appears on AMD’s recommended power supply page indicates the sum of the +5V and +3.3V ratings on the power supplies listed.  These two ratings, as well as their combined rating, are very important in choosing a power supply that will work well with your new Athlon system. 

The remaining +12V power rail is extremely important if you’re going to have any high RPM disk drives in your new system since the +12V rail powers all of the hard disks in your system.  Also, coolers such as Swiftech’s MC1000 cooler run off of the +12V rail and often times have heavy current demands which is another thing you need to take into account as you look for a power supply that can reliably power your system.

So in the end you’re going to want to look for the ratings on the +3.3V, +5V and +12V rails when looking at a power supply on paper. 

Other than the ratings there are other issues to take into account, such as cooling and the reliability of the unit itself. 

The power supply functions as a cooling device as it helps circulate air throughout your case thanks to its integrated fan.  From a cooling aspect you’ll want to look for a power supply with large holes (see right) through which the fan can pull in hot air from the case and send it on its way out. 

From a reliability standpoint, some manufacturers simply produce higher quality products which will therefore last longer under adverse conditions.  Companies such as Sparkle Power International LTD. (SPI) and Delta Electronics are well known for making high quality power supplies that aren’t prone to failure.  The cheaper power supplies often fail under high temperature conditions when under full load, and when a power supply fails during operation, the least you’ll see is a crash.  Wondering why your Athlon system crashes so much?  Maybe it’s more than just Windows 98…