22 Apr
2007
22 Apr
'07
10:30 a.m.
On Sat, 2007-04-21 at 21:37 -0500, Jack Rubin wrote:
I'm building up a demo S100 system for VCF.
I'm considering using a
modern switching power supply for regulated power and abandoning the
onboard voltage regulators on each card. I know the last CompuPro boxes
took this route so it must be feasible. What is the general
wisdom/experience with this approach?
It should work just fine, assuming you have a switching supply with
a sufficient output. I suppose you could put an inductor coil in series
to block any switching frequency current that bleeds into the supply...
but, I really don't think that is necessary if you are operating the
switching supply within its limits.
A great deal depends upon the cards you are using. When I set up my
IMSAI at the club, I borrowed quite a few 4K RAM cards from other
members, just to have a computer with the "whole" 64 K, minus 4K for the
VDM-1 video (1K) my version of a monitor & BIOS ROM routines (2K) plus
1K of scratch RAM for the monitor, which included a memory test. That
was 15 4K static memory cards, plus everything else. Yikes. It was
drawing just over 32 amps from the IMSAI +5 volt supply, which I think
was rated at 30 amps. Someone I know, out of curiosity, actually
arc-welded with the IMSAI supply.
If you do NOT have 60K of 2102 chips, you will probably be drawing a
lot less current. It would be good to know just how much your system
will be drawing, and over-do it somewhat. That was always my theory...
Peace,
Warren E. Wolfe
wizard at voyager.net