Re: Has anyone gotten an enermax PS to show PWR_FAN rpm's

In article <42F6508A.95E44E3E@xxxxxxx>, Gordon Scott
<gordsmail@xxxxxxxxxxxxx> wrote:

> timmy wrote:
> >
> > rpm monitor requires 2 leads only...the vre pin is not available
> > because the psu powers it's own fan(s)...
> >
> > On Sat, 06 Aug 2005 18:20:04 GMT, Gordon Scott
> > <gordsmail@xxxxxxxxxxxxx> wrote:
> >
> > >I'm going nutz trying to figger out why they dont use 3 pin fan control?
>
> So what exactly are you saying? whats a vre?

A power supply that supports PSU fan speed monitoring, typically
has a two wire cable (Tacho signal and GND) going to a three
pin connector. The missing wire is +12V, and the wire is missing
because the cable is only intended for monitoring and nothing
else.

An Asus tachometer implementation, has a lower limit on the
RPMs it can measure. One of my motherboards will read 1801 RPM
as 1801, but at 1799RPM, the interface reads zero RPMs. If the
Enermax fan is particularly slow, it could be reading zero for
you as well.

The reason for this lower RPM limit, has to do with the
measurement method. Some of the hardware monitors measure the
period between pulses from the fan tacho wire, and the internal
timebase counter has a limit as to how high it can count internal
time pulses. In a perfect world, the software would choose a
different scaler setting, bringing the lower RPM fan back into
measurement range - I'm not sure what the lower limit really is,
as most of the datasheets are written to be as incomprehensible
as possible.

You might try a different monitoring program, like maybe
Speedfan, on the chance that they do a better job of
programming the monitoring hardware. Maybe, due to multiple
softwares using this hardware, they are not allowed to change
how the BIOS has set up the chip ? There is little documentation
by the authors of such programs, as to how they set up the
hardware. You'll have to experiment with the different programs,
like Asus Probe, MBM5, Speedfan etc., to find one that works.

Paul
.