Well . . . freight cost alone might be justification for using switchers.
Nevertheless, I don't see a use for the regulated supplies in connection
with a bus which by definition uses on-board regulation. If the supply
actually provides the specified voltages, that's a different situation. The
typical S-100 box, IIRC, used lots of amperes, even for just one memory
board, and generated lots of heat. The average, even BIG, PC supply is not
beefy enough to support a typical S-100 box as I remember them. 8 of the 8K
SRAM boards with 2102's . . . well, you figure it out! There were other
ways to go, of course, but back in the day of the 22-slot backplane, that's
what justified the backplane's size. Power for the entire remainder of the
system was not that much.
Dick
-----Original Message-----
From: Jeffrey l Kaneko <jeff.kaneko_at_juno.com>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Tuesday, August 17, 1999 4:33 PM
Subject: Re: imsai 2
>
>
>On Tue, 17 Aug 1999 16:11:10 -0600 "Richard Erlacher" <edick_at_idcomm.com>
>writes:
>
><Stuff SNIPped>
>
>> What puzzles me is why the IMSAI folks decided to use a switching
>> power supply when the box and everything else already supported the
>needs
>> of the S-100 with the previously available and now quite inexpensive
>> unregulated supplies of yesteryear.
>
>Well, for a given wattage, switchers are smaller, lighter, and more
>economical to produce. I imagine if they resorted to the old iron-core
>transformers of yore, they would have had a difficult time finding
>a supplier for them.
>
>When they did, the part would probly cost as much as the rest of the
>materials put together. Makes perfect sense to me.
>
>
>Jeff
>
>
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Received on Tue Aug 17 1999 - 17:57:11 BST