CPU fan upgrade question

[benkeys]

I have a desktop machine that uses basically the same type of fan as you would mount on the back of the tower case for a CPU fan, except it plugs into the MOBO with a  small 4 pin connector instead of the standard 4 pin molex connector seen on power supplies. I was wanting to upgrade the fan when i change the CPU but most fans i'm finding use the PSU molex connector. I was wandering if i could just use a fan that plugs into the PSU instead of the MOBO? I have a few unused connectors on the PSU. BTW, the fan sits in a housing in front of the CPU heatsink and sucks the air out of the front and does not mount on the CPU like alot do. I really dont want to spend double the money to get a fan with the MOBO connector unless i have to..  I plan to upgrade my single core CPU to a dual core CPU, as the one i can use is only 6.00 used. I figured i could ask here as most here are knowledgeable in many many different areas.. I know some about computers, just not a whole lot.

[Owain]

the 4-wire CPU fan will have a speed sensor that reports its speed back to the motherboard and enables the BIOS to control the fan speed. If you use a fan wired to the PSU you will lose the fan speed sensing, and the BIOS won't be able to shut the system down safely in the event of fan failure before the CPU overheats. The fan will have to run at max speed all the time so the system will be noisier.

The fan motherboard connectors are usually Molex KK; you can get mobo fan splitter leads with one to two Molex KK, so cut it up and solder a mobo molex to the fan leads.