I have custom NAS unit based on Intel Atom 330 in ZOTAC IONITX-K-E motherboard. Also I have 3 3,5'' HDDs. All this staff located in CFI mini-ITX A9849 case. It has 220W power supply unit.

I want to do ugrade to Intel i3 3225 and some mini ITX motherboard. I don't need external video card and I am going to use builtin Intel HD 4000.

Will current power supply unit be enouph for i3 system? Or I need to change it to more powerfull one?



There are two ways you can get an answer to this:

  1. Measure.
  2. Calculate.

1) Is done by putting a measurement device at the power socket.

  • Check how much power your current system draws at the power socket.
  • Adjust for PSU losses. (E.g. if it draws 110 Watt at the power socket then is is likely to supply about 85 watt to your components. Assuming a decent 80% conversion at half of maximum load).
  • Check the max power used of the atom 330+ION based motherboard. Subtract this.
  • Check the max power used by your new motherboard and new CPU. Add this.

If the result is more than 220 Watt, worry.

2) Calculate.

This is easier to do since you do not need extra hardware, but it can be hard to discover how much power a given device uses. (esp. for motherboard whose manufacturers never seem to list this).

  • Start with the drives. 3x 3½ HDD uses about 3x 15 to 20 watt Watt during spin-up. (Drives use a lot more power when you turn them on. When they are spinning this drop to about 10 Watt per 3½ 7200RPM drive at idle.
  • At max power for the CPU (easy to look up at http://ark.intel.com/. (It is 55 watt) Assume the worst case during start up.
  • Add about 10 to 20 watt for a motherboard.
  • Add 3 to 5 watt per fan.
  • Add 2-3 watt per DIMM.

Your end result:

  1. Should be lower then the max rating of your PSU. (Else it might produce smoke)
  2. Should be lower than 90% of the PSU (most PSUs get very inefficient if loaded above 90% of their maximum rated capacity. Their sweet spot is usually between 20% and 80% of their maximum load.)
  3. Should not exceed max rating on either +5 or +12 volt rails. (This is sometimes a problem, usually when a dedicated GPU draws a lot from +12v. Since you are using an Intel APU this is unlikely to cause a problem).
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  • I haven't measurement device, so I used second way. I tried to calculate and got 156W. Also I found reviews for this case but for i3 530, that has 73W, so my configuration should be ok with this PSU. Thank you very much :) – Sergey Litvinov Oct 28 '12 at 11:46

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