[SOLVED] How do i change fan speed in old motherboards?

[yammCS]

How do i change fan speed on a Foxconn h55m-le?

 

[Lafong]

15 years ago, it was done by under-volting....cutting volts supplied to the fan from 12 to either 7 or 5, using adapters made for that specific purpose.

 

[drea.drechsler]

How do i change fan speed on a Foxconn h55m-le?

Old PC's didn't use the small 4 pin fan plugs but instead got their power from floppy molex power plugs. Those plugs had +5V wire (yellow) and a +12V wire (red) from the PSU. You could unpin the +12V wire on the fan plug and move it to the cavity to connect to the +5V wire. If you're fan was good enough quality it would start and run at just under 1/2 of full speed.

Low quality or older fans frequently didn't start without spinning them first since 5V didn't generate enough torque. What you could do then is remove the ground pin and move it to the +5V pin, but leave the +12V pin in place. That would give you +7V, usually enough to start and run the fan at a little over 50% speed.

But the smart people got, or built, fan control hub kits with a rheostat to physically control each fan in the system. They'd fit in place of a floppy drive. Something like this:

Lamptron 5.25" 6-channel fan controller, 45w/channel, 3-pin fan & molex power connector - Newegg.com

Or even in an unused I/O slot in back. But that made it inconvenient to tweak a fan when the CPU was running warm.