Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watmath!clyde!rutgers!sunybcs!bingvaxu!leah!uwmcsd1!csd4.milw.wisc.edu!neighbor
From: neighbor@csd4.milw.wisc.edu.UUCP
Newsgroups: comp.sys.apple
Subject: Re: Expansion Box
Message-ID: <3781@uwmcsd1.UUCP>
Date: Thu, 3-Dec-87 22:39:44 EST
Article-I.D.: uwmcsd1.3781
Posted: Thu Dec  3 22:39:44 1987
Date-Received: Sun, 6-Dec-87 20:20:38 EST
References: <8712021731.aa12058@SMOKE.BRL.ARPA>
Sender: daemon@uwmcsd1.UUCP
Reply-To: neighbor@csd4.milw.wisc.edu.UUCP (Jeffrey Alan Ding)
Organization: University of WI-Milwaukee
Lines: 29


Ray,

  Your expansion box will cause more problems than you realize.
Each line coming out of the connector has loading limits.  This means
that you can only hook up so many TTL gates to each line.

For example.  I think the Address lines can only handle 2 TTL loads each.
    (I don't quite remember, don't have the reference manual in front of
     me.)
     If you have cards in each of your 4 slots that you made on your
     expansion box,  assuming only 1 load per slot per address line,
     you will have 4 loads on each address line.  That is twice the
     limit.

There are other lines that I think can only handle 1 TTL load.

If you overload these lines your computer will malfuntion and not operate
correctly.  I have experience with this problem.

You should also have these lines buffered.  They all should be
buffered.  Also if the cable going from your expansion box to the computer
it too long you will also develop timing problems.

The only way to get around this problem is to switch every line with
elctronic gates.  This is probably the only way that your expansion
box will work trouble free and reliably.

neighbor@csd4.milw.wisc.edu