I have got 650 watt power supply unit. It has a lot of SATA cables. There is two cables, both splits to 4 molex connectors. Two molexes are used for my two optical drives. 3rd one is used for ATI Radeon HD 4650 (AGP) and there is an 80 mm case fan attached to that molex. So that calbe leaves one molex free.

My question: is it safe to add 40 mm fan to that molex?

Both fans are from Xilence.


This cannot be answered properly without information about your power supply and its current load on the rail.

A fan is usually 5 watts.

So take your PSU info, see maximum load on the rail, calculate your current usage and if you have more than 10 watts to spare it should be OK.

  • @surfasb Can you elaborate a bit on that analogy? – D.Iankov Sep 24 '11 at 18:38
  • You can calculate the maximum number strings of Christmas tree light that you can daisy-chain by adding up their power-usage and comparing that to what the outlet supports. – Bobson Sep 24 '11 at 18:55
  • @Bobson: The question is asking whether it is safe, but Bobson has the right idea. The Christmas tree is a Political Science slang for a Bill that has enough adornments to where one more adornment could have it fall over. Without knowing what else is already on it, you have no idea where is the breaking point. – surfasb Sep 24 '11 at 19:00
  • Oh okay. I had not heard of the political analogy. I was thinking of the actual lights (I guess I am getting old). :-D (The bill analogy reminds me of some shows or movies: ...and now we vote on the next bill to provide cheap health-care and funds for public schools; oh and senator so-and-so has attached a rider to reduce sentences for child-molesters. All in favor?) – Bobson Sep 24 '11 at 19:04

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