Q: I'm a bit confused here.. my PSU has 2 +12V voltage readings on the label. The two readings are labeled as "12V-1" and "12V-2". The 12V-1 has 14amps and the 12V-2 has 15amps.. Does that mean I have a total of 29amps on the +12V rail? Also, is it a good thing or bad to have 2 +12V readings? There's also a "-12V" label, which has a very low amperage. I'm tryin to buy a Radeon x1650pro, so I need to get this voltage thing cleared up before I take another step. My system specs: Intel Celeron 2.53ghz 1gb RAM (1 stick DDR2 SDRAM) Radeon 9250 128mb PCI card Coolmax 350w PSU
A: Coolmax... wince. According to the label, you should have about twenty five amps on the 12 volt rail. See, you sum up the 12V rails, but then add in a good 15+% safety margin to account for bridging or something of that nature. However, since it's a coolmax, I question if it really kicks out that much without heinous ripple (and corresponding crashes) or really hot exhaust. JonnyGur's OEM list tells me that their supplies are made by ATNG and Sirtech, middling at best companies, but the really cheap prices on CoolMax's cheaper units make me wonder just how many corners were cut, or if CoolMax doesn't have an even cheaper line made by Leadman or Deer. The supply may safely power a 9250, and even a X1650 will probably work Ok for a while with it, but if it were my system, I'd pull the supply and put in a 30$@Newegg Antec Earthwatts 430. I would have reccomended another video card, but I suppose you have AGP. The rest of your question: -12V provides some kind of phantom power to your system. Nobody ever seems to reference it when assembling, so I think that spec can be ignored. Pretty much all power supplies over about 300 watts now list multiple rails. With power distribution shifting from 3.3V and 5V to 12V, it really makes sense, especially for 500+ watt units. You may then ask, but why does a feeble 350 watter have two rails? That's because most supplies start as a generic board, with room for different size parts to make cheaper and weaker or stronger and more expensive supplies. These things are custom order for companies like CoolMax, and many OEMs will gladly do anything, down to an alarmingly common willingness to strip out most if not all power safety equipment.