3 Replies Latest reply on Jul 19, 2010 7:08 PM by Harm Millaard

    Final selection of PSU & UPS


      Figured I'd start a new thread on this since it's important.


      Can someone please look at the attached PSU Calculator file and tell me if I'm **** this right.


      PSU Calc.1.jpg


      I've circled the areas I have questions about.


      1) CPU Utilization

      2) Overclocking

      3) USB Devices (I assume this is how many devices are plugged into external USB ports that get power from the port? And would not include my printer which is communication and not power?)

      4) System load

      5) Capacitor aging (can someone explain this?)


      I was planning on a 1000W PSU. Do these numbers indicate that I should look for higher since I'm at the top end now?


      I also just realized that I did not include the additional 2 fans that will be part of the CPU cooling system.

        • 1. Re: Final selection of PSU & UPS
          Harm Millaard Level 7

          There is a very good explanation about capacitor aging on the website, but it boils down to this:


          Every PSU, like everything you use, will show sings of wear and tear in due course. Like the tires on your car, your washing machine, your TV, everything that you use will degrade over time and ultimately break down and will need a replacement. Same with a PSU. The things that cause a PSU to break down are the capacitors and these lose their capacity just as surely as the battery in your car. If you have a 4 year old battery in your car and one day it does not start, you can know it is the battery. To avoid problems with the PSU failing in the intended life you envisage when building a new computer, which may be 3 to 4 years, you have to calculate loss of power in the intended life span, and that is what capacitor aging is about. If you read the notes at the bottom of the page you will see what it means, depending on whether you use your system 24/7 or only for a few hours per day.


          You did not use the Pro version, which I highly recommend, because you don't have the required amperage per rail now, which may decide your choice of PSU. Additionally, you used 1.45V for the 930 overclocked, which is pretty high @ 3.8 GHz, so from the looks of it you may get by with a 1000 W PSU, but I noticed you did include a 56K modem? Your settings were at 90% CPU load if I read the screenshot correctly. What does it say when using 100% CPU load?


          To be safe, I would look at a 1200 W PSU. For a UPS, look at a model that delivers at least 1.5 kVA, but possibly 2.2 kVA.

          • 2. Re: Final selection of PSU & UPS
            magneter Level 1

            Thanks Harm


            I missed those explanations at the bottom. Yes I know about the modem


            I'm in the Pro version now.

            With 100% CPU load

            Overclock CPU speed still at 3800, lowered voltage to 1.20


            Also have system load at 100%


            Min PSU: 924

            Rec: 974


            Minimum UPS rating: 1391 VA
            Recommended UPS rating: ** 1750 VA

            • 3. Re: Final selection of PSU & UPS
              Harm Millaard Level 7

              @ 3.8 GHz, you voltage may be around 1.25 - 1.275 V. Anyway it looks like your minimum PSU needs to be at least 1,000 W and the UPS at least 1.5 kVA. If you have relatively unreliable electricity supply (meaning over 2 failures per year) you may opt for the 2.2 kVA version UPS, such as this one: APC Smart-UPS 2200VA USB & Serial 230V.