Question on power supply part

[tenest]

wasnt sure where else in anandtech to post this question...

on (at least) the last three power supplies, i've noticed an "extra" connection but i can not for the life of me figure out what it is for. it's a 3 wire connection that ends in a plug that would typically fit into a fan header on the motherboard. i cant find my multimeter so i cant check to see what kind of voltages are coming from each of the three wires. i have seen this is exact same connection on an antec, enermax and powermax (oem) brand power supplies.

anyone have a clue as to what this for?

oh yeah, all the power supplies i've seen this on are P4/AMD XP capable.

 

[bozo1]

It is to plug into a mobo fan header. Some Enermaxes use that to power and monitor the 2nd fan. Some supplies with only one fan use it so you can monitor them as well.

 

[SnowPunk98]

Yep its for RPM monitoring

 

[HappyPuppy]

That terminal is for monitoring the psu fan rpm. I don't think it powers the fan, though.