add-on CPU load meters

From: Brian Knittel <brian_at_quarterbyte.com>
Date: Fri Dec 28 17:10:39 2001

There was an analog CPU meter on a PDP 11/70 in the Computer Graphics
Lab at UC San Francisco back in the late 70's. The meter was mounted
in the middle of a large black & beige plastic rack fill-in plate. I
thought it was hilarious, and very cool. It has to be an analog
meter.

I dimly remember seeing the schematic. The meter was wired up as a
dwell meter, and hooked up to some signal in the CPU that indicated
that it was running, or at least running usefully. I can't remember
if it was the user-mode bit, or "not wait". IIRC Unix V7 ran an idle
process so the CPU never waited. I think it was the user-mode bit.

Anyway, the circuit was simple. They buffered the CPU signal,
smoothed it through a resistor and a capacitor, and that drove the
panel meter. You just have to work out the appropriate values for the
series resistor, capacitor and load resistor to get appropriate
scaling and timing.

I've always wanted one... wonder if there's an appropriate pin
to monitor on a TBird?
Received on Fri Dec 28 2001 - 17:10:39 GMT