NCR model 3401 class 5451

From: Dave McGuire <>
Date: Thu Jun 22 02:02:12 2000

On June 21, Tony Duell wrote:
> > > ps margin: +5%/normal/-5%
> >
> > What's a ps margin switch for?
> Power Supply Margin testing, I guess. Basically it runs the PSU (+5V
> line, probably) at 5% over or under the 'right' value. If you have an
> intermittant fault to trace, this may make it appear permanently so you
> can track it down. Similarly, a machine that fails on either of the
> margin settings is likely to _become_ unreliable even at the normal
> voltage, so you can catch errors during preventive maintenance.

  Interestingly, both the Cray J90 and the YMP-EL (and possibly other
models as well) have +- margin switches for their power regulators
accessible on their front panels.

        -Dave McGuire
Received on Thu Jun 22 2000 - 02:02:12 BST

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