Percival P. Cassidy wrote:
I have an Asus Prime Z370-A motherboard that has several different fan
connectors, but only two for "Chassis fans."
I have the top and rear fans connected to CHA_1 and CHA_2, respectively,
but I am wondering whether to connect my two (non-PWM) front mounted
drive-bay fans to one of the other on-board fan-connectors or whether to
just power them from a Molex connector.
The currently unused on-board connectors are CPU_OPT (intended for
dual-fan coolers, I think), AIO_Pump (which does not seem to have any
kind of speed sensing control, and M.2.
Suggestions?
Perce
The fan headers look equally functional. There's six 4-pin
connectors with PWM and RPM. The 5 pin has signals for PWM
and RPM for two more fans (but no +12V), intended for external
fans of some sort.
https://dlcdnets.asus.com/pub/ASUS/m...0-A_UM_WEB.pdf
If you went by the electrical information they provided, it
looks like a total of 8 channels worth. They can do this, because
they're getting these channels "for free" from somewhere. Maybe some
on PCH, some on SuperI/O or something. In the old days, they
didn't like to make "controlled" headers, because it cost
a pass_transistor for each one. These headers today only
contain logic signals (plus raw power). Only the gold header
pins cost money in a sense.
None of those headers should be modulating +12V. The +12V
should be straight thru. The PWM signal enters the fan
hub, and sets the speed at that point. Rather than the
motherboard having any voltage related circuits on board.
If it's more convenient, you can run the drive bay fans
off a molex. Not every fan has RPM output, so some fans
can't be monitored in any case.
Looking at the BIOS screen, might hint that
what's in the manual is "fake" or not. You might
take your queue from what you see in there. Or
if Speedfan doesn't list everything, then some
of the headers might be four pin... but with
no electrical connection to RPM or PWM. That might
happen if the hardware didn't happen to have that
many signals just "lying around".
Paul