22 Jan
2009
22 Jan
'09
3:02 p.m.
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-
bounces at classiccmp.org] On Behalf Of Roy J. Tellason
Sent: Thursday, January 22, 2009 10:41 AM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Running 3 phase 780s on single phase power
On Wednesday 21 January 2009 02:42:35 pm Gordon JC Pearce MM3YEQ wrote:
seem
Or, it's the difference between pragmatism and historical preservation. We try
to preserve the system as closely to its history as possible, while recognizing that
sometimes compromises are necessary. Sometimes, those compromises even reflect history:
for instance, the replacement of linear supplies with switching supplies in PDP-10s, which
seems to have become common practice as the model line matured. Our goal is always to
have a system someone can _use_, as we work to develop a 'best practice' that
addresses that while maintaining the historical integrity of the original machine. --
Ian
On Wed, 2009-01-21 at 19:13 +0000, Tony Duell
wrote:
> > > Umm. No. That transformer is a ferro-resonant transformer. It
> > > *needs* 3-phase to work! It supplies the basic 12v DC that are
then
> > > used to by the linear regulators.
It's those that burn the
power as
> > > heat. Replacing the linear
regulators with switchers will
reduce the
> > > consumed power by a lot.
> >
> > Since extremely high current switchers are relatively cheap (at
least
> > compared to getting three-phase
installed, and massive aircon
systems),
> > is there any reason why you
*wouldn't* go down this route?
> > Particularly for a machine that's going to be on a lot?
>
> Err, historical accuracy? The PSU is as much a part of the system
design
> as the CPU (OK, maybe I exagerate, but not
by very much). I know
that if
> I owned a large adn rare machine (large VAX,
PDP10, etc), I'd want
to
keep it
as original as possile.
That's all very well, but if it costs you three times as much to run
because of the huge inefficient power supply then it all starts to less practical. That's the sort of thing
that makes the difference
between a viable system that you can actually use and enjoy, and a
bulky
ornament.
I guess that's the difference between wanting something so you can
_have_ it
vs. wanting something so you can _use_ it.