I just upgraded my CPU/Motherboard (Athlon XP 2500+ / MSI K7N2G-L) and I also had to get a new power supply, since the old one didn’t have the right connections for the MB power.
On the MB are 2 fan connectors, one for the CPU fan and one for the “system fan.” One of the cables coming out of the power supply is a fan connector, which I plugged in to the system fan connection. On the BIOS display it shows the RPMs for both the CPU fan and the System Fan.
My question, is this really needed for the power supply fan? Shouldn’t it get power directly from the power supply? Or is the connector merely a means to monitor the fan and maybe speed it up and slow it down as needed?
Bottom line, should I leave this connected or remove it?
That sounds to me like a means just to monitor the fan speed. It might be a good idea to leave it connected because the motherboard may shut off to prevent damage in case the fan stops or slows in the power supply. Did you have to get a P4 power supply with the 2 plug power connectors? Looks like a nicely equiped motherboard.
If you can post your motherboard and power supply model numbers, I may be more helpful.
My guess is that the fan connector coming out of your power supply allows the motherboard to send differing amounts of voltage to (one of?) the PSU fan(s) based on internal temperature of the machine. You could just as easily attach a third-party fan (case fan, RAM fan, vid-card fan, etc.) to the ‘system fan’ prongs on the motherboard, and the motherboard would then control that fan instead.
Read your motherboard’s manual to find out where the ‘system temperature’ thermistor/temperature probe is; for best results, the fan you plug into the ‘system fan’ prongs should be located near that probe. Otherwise, your motherboard will be changing the speed of a fan based on an unrelated temperature measurement.
I suspect that the fan wires running to your PSU are for a second fan in your PSU, or perhaps just to feed the motherboard’s recommended fan speed to the PSU. Whether the PSU complies with this number is a matter of design.
See the OP for the motherboard model number. I don’t have the model number for the power supply handy, but it’s a generic CompUSA 250W ATX power supply with a single fan. Actually, I swapped PSU’s with my son’s computer, since his had the Pentium 4 power connectors which he didn’t need and I did.
Not to be a killjoy, but depending on what else you have in your computer (1 hard drive or 2, 1 CD drive or 2, etc) you may want to get a higher amount of watts.
I just finished putting a computer together, and even for something without all the bells and whistles, I was gleaned from my research that a P4 should be coupled with at least 300 watts if not more. This was thinking forward though, as I plan to add more devices down the road that will suck down electricity from the PSU.
Why did you need a P4 power supply to feed an Athlon? (Or did the P4 supply also have the Athlon-specific extra power connector?)
Whatever you do, be sure to use some means of monitoring the CPU fan’s speed. (eg: Motherboard monitor) Athlons are notoriously fragile, and if the CPU fan stops, the CPU tends to burn to a crisp in a few seconds.
Pentiums are smart enough to simply slow themselves down or even turn off if they get too hot.
And yes, 250 watts is marginal. If you start having any weird problems like spontaneous reboots or hangs, get a good name-brand (Antec, PC Power & Cooling, etc.) PS of at least 350 watts.
The motherboard for the Athlon has the standard 20-pin ATX power connector, but there is also a separate 4-pin square connector to provide 12V to the CPU. This is a standard feature on newer power supplies designed for the P4, but did not exist on older ATX power supplies.
The MB does monitor the speed of both the CPU fan and the System fan as well as CPU temperature, and presumably will take appropriate action if tolerances are exceeded.
As far as devices, I have one HD, a DVD-ROM and a CD-RW. I probably will upgrade to a beefier power supply soon, but for now I will have to use what I’ve got.