S-100 bus termination

From: James Willing <jimw_at_agora.rdrop.com>
Date: Sat Jul 25 11:36:32 1998

At 07:26 PM 7/24/98 -0500, you wrote:
>I was digging through some S-100 cards and came upon a Godbout active
>terminator. Do all S-100 buses require external termination, or did more
>have it built into the mobo?

Originally, the Altair (S-100) bus did not define a need for termination of
any kind. It was not until things on the bus started to speed up (using
DMA and such) that anyone apparently thought about it.

A number of companies started to put out terminator cards (active and
passive) that just plugged in, and later some manufacturers (Gotbout being
a notable example) began to incorporate (active) termination into their
backplane boards.

>Specifically, do I need to stick this card into my IMSAI?

Can't hurt. I will say however, I do seem to recall seeing a board or two
that would not run on a terminated bus, but that has been so long that I
don't evem recall what it was.

A note tho: if it is an active terminator, check the regulator voltages and
filter caps on the board with no other boards in the machine. A bad
terminator can introduce many more problems that it will solve.


The Computer Garage - http://www.rdrop.com/~jimw
Computer Garage Fax - (503) 646-0174
Received on Sat Jul 25 1998 - 11:36:32 BST

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