Shared Knowledge


ďHow to: Select a PC Power Supply (Watts)Ē


20 February 2007



Summary: A PC power supply can be had for as little as $20 or it can cost as much as almost $1000. What? Why not just buy the $20???






Suspect most folks do not even know what size (in watts) power supply they have in their personal computers (PC) and what does it matter if their PC works? Well, for sure, some PC users never upgrade their hard drives or add additional hard drives or DVD or CD burners, or memory or faster video cards, but some of us do.


Been into plenty of PCís over the years and amazing what I find. Donít understand or actually I do, why a manufacturer would put a 90 watt power supply in a PC or a 200 watt. While these may work for the configuration they are selling, these size power supplies just wonít cut it if the user adds to or changes much of anything.


Now in my case, I build my systems from scratch and my main machine uses an Intel motherboard, 3GHZ processor and I have 2GB of PC3200 memory, 2 hard drives, a CD burner and a DVD burner and 3 case fans besides the fan on the power supply and the fan sitting right on the CPU chip. When I built my system, I knew I was going to need a supply which provided an extra 12 volt connection to the motherboard and also one, which had a thermostatically controlled cooling fan. So, given all this and not into actually calculating loads for the various voltages supplied by the power supply, I settled on a top of the line, 465watt.


Since building my main system, all has been well. I have had no problems related to power or I didnít until I tried to add a new 500GB SATA drive tonight. At first it appeared that the power supply could handle my entire load but then a sudden system shutdown and restart and then another. So unhooked the SATA drive and booted again. After the scandisk operation and then another one right after that, the system is now stable again but obvious that I need to upgrade my power supply from my current 465.


500? 600? 750? 1000? From researching, it would appear the world is awash in PC power supplies and like just about everything, it is hard to be able to get a decent comparison between any 2 in terms of amps supplied at various voltages.


Recently, I worked on a Dell 8200, which was made in 2000. Although had not planned on it, wound up replacing hard drive, memory, video card and CD burner and after finding out that the system only had a 200watt power supply in it, upgraded that too to a 600watt model. No problems with that unit now but was disgusted that Dell saw fit to not have a master switch on their power supplies and thus any off the shelf supply would not fit because there was no place in the case for the master power switch, which is standard on any off the shelf supply today. Well, could have paid Dell or one of the third party supplies a fortune for a supply that would have just dropped into place but I just could not do that and so I cut out a chunk of the back case to accommodate an off the shelf supply with master switch. What would it have cost Dell to have put a master switch in their power supplies? Another dollar or 2?


Back to my system. As I have on order a new video card with 512MB of Ram on it and I already know that my 465 wonít cut the add of another drive, just going to go with a 750watt. Probably more than I need but who knows what I might do tomorrow. Still have a connector for another SATA drive and space in my full tower case.


Guess the bottom line here is, if you are thinking of adding more drives or upgrading your video card or adding more memory, you better take a look at the size of your power supply as you might have to upgrade that as well. And given my experience tonight, if you upgrade some components and the system starts becoming unstable on you, donít forget that it could be the power supply crapping out on you.