I'm building a new PC and the thing I'm having the most trouble with is which power supply to buy.

I'm used to thinking "the more watts the better", but people have told me I have to think about amps too. But then I can't find any info on amperage, and I get even more confused. ARGH!

So I was wondering if you good people could just suggest A power supply. Not what kind, not a brand you like, an actual single product.

I'd like as much power as possible. I'm going to have an AMD 2100+, two CD drives, two 3.5" drives, possible future RAID 5 config (3 drives) plus my 100GB IDE drive, and some other stuff. I'd just like to get as powerful as possible to accomodate any future expansion. I'm willing to go up to around $150.

Please help!

The one I use: Enermax EG451P-VE

It's been rock solid, and should have enough power for your needs. I've got a AMD 1.4Ghz, DVD drive, CD burner, 4 IDE drives(going up to 6 soon), and the power supply runs nice and cool.

Okay, I have a question about Enermax power supplies. something like this:



is the side with the larger fan considered the bottom or the top, relative to its installation in the PC case?

The reason I ask is because I'm not quite sure if the case I have will work with a fan on the bottom...

*edit* I guess that fan isn't really larger, but I'm talking about the one on the larger side of the PS. also, I checked, and on the back of my case, the fan will be on the left, and the other stuff on the right. that would defeat the purpose of that large-side fan, wouldn't it?

Power supply mounting depends on the case. I use mainly In-Win cases and they will properly mount that power supply.

I have another case here that will not. It seems that a reasonable way to be sure is if the IEC connector on the original power supply is on the left or right when mounted in the case. If the connector is on the left, you should be good.

> I'm used to thinking "the more watts the better", but people have told me I have to think about amps too.

Perhaps I am missing something here, but since watts = volts * amps, and the output of a power supply is always the same number of volts (5 or 12 I believe, depending on what it is powering), than more watts does = more amps.

In 99% of installs the fan points down towards the processor

Unfortunately, this is not so in the case I bought. With the fan hole on the left and the power stuff on the right, that would mean the fan points up.

So are there any other suggestions for products?

That's only true in DC power. Since AC power drain includes impedance (and, obviously, the power is running in a waveform), the waveforms of the volts and amps are not aligned. This leads to variable wattages in an AC power line, even some that are negative, conceivably. In fact, the mythical perfect inductor would actually draw no watts, alternatingly drawing and pushing back the same amount continuously.

I'm probably doing a poor job of explaining it, so check out this page on power factor, which is inextricably linked to what I'm trying to talk about here, as power factor is the ratio of Watts to VoltAmps. He does a good job of explaining it, I think.

Edit: Then again, motherboards and other inside-the-case computer devices should be drawing DC power, so what do I know? Maybe the Watts are measured at the mains-side and other stuff is measured elsewhere. Regardless, that power factor stuff is interesting to know, so I haven't totally wasted my time.

I'm used to thinking "the more watts the better", but people have told me I have to think about amps too.

Perhaps I am missing something here, but since watts = volts * amps, and the output of a power supply is always the same number of volts (5 or 12 I believe, depending on what it is powering), than more watts does = more amps.

The point is that, while a PSU may provide (say) 450W altogether, it's still not much use if its 12V output is at 425W and its other outputs (5, 3.3) only add up to 25W. Dignan's advisers were asking him to check whether the amperage on each individual voltage line was sufficient for his system. (AIUI, hard disks and fans need 12V amperage, general PCI cards and logic 5V, and CPUs and AGP cards 3.3V, but I'm prepared to be corrected on that.)

So, for instance, if you have two CPUs at 50W each, you'll need at least 100W available on the 3.3V line, which is 33A.

Peter

Thanks, I ended up with an Antec True550. It was $50 less than an equivalent Enermax I was looking at. We'll see how good it turns out to be...

Antec is a good power supply, dependable, enermax is a little prettier but it's going inside right? so who cares. After that last post I realized I have a case in which the fan actually sits sideways... so scratch the 99% that I said earlier and lets say 60%? sounds good to me

Antec PSU's are cheaper because Enermax PSU's are specifically built to be low-noise. Most Enermax models even have a manually ajustable fan. (the speed of the fan can be altered with a little knob on the back op the PSU - of couse the slower the fan, the less noise it makes)