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From: hah@omepd.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: Expansion product woes
Message-ID: <521@omepd>
Date: Sun, 29-Mar-87 14:01:46 EST
Article-I.D.: omepd.521
Posted: Sun Mar 29 14:01:46 1987
Date-Received: Tue, 31-Mar-87 01:18:19 EST
Sender: news@omepd
Reply-To: hah@isum.UUCP (Hans Hansen)
Organization: Intel Corp., Hillsboro
Lines: 38
Keywords: Too many loads!!



I have been very quiet here so far but I feel I must correct a few erroneous
assumptions made by some of the hardware designers.

Assumption 1 : I can have as many TTL gate loads as I want on the output
lines of the ZORRO BUS.

A)  The Zorro bus std allows for only one LS gate load per line.


Assumption 2 : Passing the buss thru a board is a good idea.

A)  All boards that pass the buss thru may only have one LS load per line
and therefore will work fine by themselves.

Adding one or more boards with pass thrus adds additional LS loads
because the first board does not buffer the signals before they were
passed thru and neither do the remainder of the boards.


Assumption 3 : As a designer I dont need to read all the fine details of
the ZORRO BUS specs.

A)  The Zorro spec is also quite clear in stating that the maximum length
any output trace to buffer can have.  (I'm sorry but I do not have the specs
with me now.)


My point in this is quite simply to point out that while a single board
by itself will work perfectly, as soon as a second board is attached to
the first boards pass-thru buss they both violate the Zorro bus specs.

If you as a user need to have more than one expansion board on your
system then you must use one of the CORRECTLY buffered expansion boxes.
NO EXCEPTIONS!!

Hans