Xref: utzoo unix-pc.general:2004 comp.sys.att:5118
Path: utzoo!attcan!uunet!lll-winken!ames!mailrus!rutgers!mit-eddie!killer!osu-cis!n8emr!uncle!jbm
From: jbm@uncle.UUCP (John B. Milton)
Newsgroups: unix-pc.general,comp.sys.att
Subject: Re: 1 or 2 part upgrade
Keywords: 3b1, 2-disk upgrade, HwNote, P5.1 PAL
Message-ID: <458@uncle.UUCP>
Date: 7 Jan 89 04:13:39 GMT
References: <413@limbic.UUCP> <450@uncle.UUCP> <417@limbic.UUCP> <10@taqwa.UUCP> <7362@chinet.chi.il.us> <4578@mtgzy.att.com>
Reply-To: jbm@uncle.UUCP (John B. Milton)
Organization: U.N.C.L.E.
Lines: 26

In article <4578@mtgzy.att.com> rlf@mtgzy.att.com (r.l.fletcher) writes:
[both upgrades on one board]

I thought long and hard about it, and it would work as you describe: only
populate or enable the part you want. Putting the P5.1 PAL on my board would
mean 4 more wires from the board to the UNIXpc mother board:
1. D0
2. D4
3. /PHSTAT strobe
4. /HDSEL3 output (not really, since it goes to the 34 connector on the board)
The /RST, /MCR2SEL, Vcc, GND are already on my board.

I guess it's not that bad for people who don't ALREADY have the P5.1 installed.
As far as chopping the mother board up it would mean not desoldering 22 holes
and solding them back again. The left fan grate is close to that corner of
the board, so the wire length would not increase too much. I would not hack up
my design to try to integrate all this stuff into one PAL, rather I would have
a regular P5.1 PAL and my PAL. This would make my design 4 chips total, same
size board, same place, same connectors.

I will look at it tonight and post a follow up.

John
-- 
John Bly Milton IV, jbm@uncle.UUCP, n8emr!uncle!jbm@osu-cis.cis.ohio-state.edu
(614) h:294-4823, w:764-2933;  Got any good 74LS503 circuits?