Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ucbvax!CLUTX.CLARKSON.EDU!bh0r
From: bh0r@CLUTX.CLARKSON.EDU (Rob Logan)
Newsgroups: comp.sys.zenith.z100
Subject: Re: More Memory for old Z100
Message-ID: <8801221415.AA28396@clutx.clarkson.edu>
Date: 22 Jan 88 14:15:31 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 214

I wrote this TeX file for a class last year. It will is the patch
to put 768K on an old Z100.

--------------------------------------------------------------------
% History:61
\documentstyle	[12pt]	{report}
\begin	{document}

\begin	{titlepage}
\title	{Adding 256k chips to\\
	 your older Z--100.}
\author	{Robert Logan \\
	 Paper 6 \\
	 TC 210--01}
%\date	{\today}
\end	{titlepage}
\maketitle
%\baselineskip 24 pt

\vspace	{1 in}
\centerline	{\Large \em Audience Analysis}
\vspace	{2 in}

This modification is not intended for a beginner. It assumes you have a strong
electrical background. Experience building pc boards is necessary.

\newpage
\vspace	{.25 in}
\centerline	{\Large \bf Adding 256k chips to your older Z--100.}
\vspace	{.25 in}

\centerline	{\Large \em Before we begin.}
\vspace	{.25 in}

Before we get started you need to collect the following:

\begin	{centering}
\begin	{description}
\item	[1]		16 pin socket.
\item	[1]		20 pin socket.
\item	[1]		33 ohm resistor.
\item	[1]		74LS257
\item	[9, 18 or 27]	41256 RAM chips.
\item	[5']		26ga wire.
\item	[1]		soldering iron.
\item	[1]		181--4918 or earlier Z--100. {\sf Note: Computers with a
later model number (found near the parallel port) just new PALs.}
\item	[1]		1' solder. {\em Caution: Do not use acid core solder.}
\item	[1]		Large work bench.
\item	[1]		1 hour of time.
\end	{description}
\end	{centering}

For you absent minded hacks that forgot pins of a chip are numbered starting
from the upper left hand corner counting counter clock wise around the chip,
here is a table:

\newpage
\vspace	{.25 in}
\centerline	{\Large \em Getting things ready.}
\vspace	{.25 in}

\begin	{description}
\item	[(  )]
Disassemble your computer following the instructions provided in your Z--100 Users
Manual pages 3--10.

\item	[(  )]
Remove the main board totally from the computer case by removing the 10 screws
and the card cage.

\item	[(  )]
Place the board a large work bench.
{\sf Tip: Put a dry towel on your table under the board so it does not slip.}

\item	[(  )]
Identify U111, U146 and U173, these are the chips we will be working with.

\newpage
\item	[(  )]
Remove U101 through U109 (bottom 64k of RAM)
\item	[(  )]
Remove U117 through U125 (middle 64k of RAM)
\item	[(  )]
Remove U137 through U145 ( top   64k of RAM)

\item	[(  )] Flip the board over and identify pin 1 of the all the RAMs U101
through U109, U117 through U125 and U137 through U145.  {\em Caution: remember
the pins are reversed if you are looking from the bottom.}

\item	[(  )]
Solder a continuous wire to all RAM pin 1's

\item	[(  )]
Leave about 5" of wire and flip the board over, chips side up.

\item	[(  )]
Install U101 through U109 with new 41256s (bottom 256k of RAM).

\item	[(  )] Install U117 through U125 (if you have them) with new 41256s
(middle 256k of RAM).

\item	[(  )] Install U137 through U145 (if you have them) with new 41256s
(top 256k of RAM).

\vspace	{.25 in}
\centerline	{\Large \em The U146 modification.}
\vspace	{.25 in}

\item	[(  )]
Take your 74LS257 and cut off pins 5, 6, 7, 9, 10, 11, 12, 13 and 14.

\item	[(  )]
Bend out vertically pins 2, 3, 4 and 15.

\item	[(  )]
Verify that pins 1, 8 and 16 are the only pins left sticking down.

\item	[(  )]
Solder a wire from pin 15 to pin 8.

\item	[(  )]
Solder a 5'' wire pin 3.

\item	[(  )]
Solder a 5'' wire pin 2.

\item	[(  )]
Solder one end of the 33 ohm resister to pin 4.

\item	[(  )]
Solder the wire from the RAM's pin 1 to the other end of the 33 ohm resister.

\item	[(  )]
Pull the 74LS257 at U146 and solder the new 74LS257 to
the top of it with pins 1, 8 and 16.

\item	[(  )]
Inspect the new piggy backed chip for shorts and reinsert it into U146.

\vspace	{.25 in}
\centerline	{\Large \em The U173 modification.}
\vspace	{.25 in}

\item	[(  )]
Pull the PAL at U173.

\item	[(  )]
Bend up pins 1 and 2.

\item	[(  )]
Solder a jumper from 1 and 2 to pin 10.

\item	[(  )]
Take your 20 pin socket and solder a 5'' wire into the hole were pin 1 would
have gone.

\item	[(  )]
solder another 5'' wire into the hole were pin 2 would have gone.

\item	[(  )]
Install the PAL into your new socket.

\item	[(  )]
Inspect the new socket/chip pair for shorts.

\item	[(  )]
Install the new socket/chip pair back in to U173.

\vspace	{.25 in}
\centerline	{\Large \em The U111 modification.}
\vspace	{.25 in}

\item	[(  )]
Remove the Memdec chip at U111.

\item	[(  )]
Bend up pins 2 and 3

\item	[(  )]
Solder the wire from the socket pin 1 of U172 to pin 3 of U111.

\item	[(  )]
Solder the wire from the socket pin 2 of U172 to pin 2 of U111.

\item	[(  )]
Solder the wire from the top 74LS257 of U146 pin 2 to the 3 hole
of the 16 pin socket.

\item	[(  )]
Solder the wire from the top 74LS257 of U146 pin 3 to the 2 hole
of the 16 pin socket.

\item	[(  )]
Install the Memdec chip into its 16 pin socket.

\item	[(  )]
Inspect the assembly and insert the modified Memdec chip back into U111.

\end	{description}
\vspace	{.25 in}
\centerline	{\Large \em Finishing.}
\vspace	{.25 in}

Wow you did it!!! 
Put the Z--100 back together using pages 11--18 of your Z--100's User's Manual.
{\sf Tip: You might consider using your ``old'' 4164 chips in your video card.
If you do remember to change J307 down, J305 and J206 to the left.}

\end	{document}

--------------------------------------------------------------------

				Rob