jeb6589@ritvaxc.BITNET (Jim Berg) (04/21/86)
The 130XE/320K upgrade
by Scott Peterson.
(revised and tested version, revised and tested by who
I don't know - Jim)
After both reading and building both the 800/288K
upgrade (D.G.Byrd), and the 800XL/256K upgrade (C.Buchholz),
I decided that there also had to be a way to upgrade the
130XE. There is, and thanks to the "Freddie" chip (CO61991)
this modification is much easier to do than either of the
other upgrades.
To do the upgrade you will need a soldering iron, a
de-soldering tool, and some fine wire. See the parts list
for the chips needed.
First, remove both the case and the metal shield to get
down to the mother-board. Then remove the eight ram-chip
U26 thru U33 (MT4264). They are the row closest to the TV
RF module. Next, bend up pin 1 on Z2 thru Z9 so that they
point straight up and do not contact the PC board or
sockets. Now install Z2 thru Z9 in the place of U26 thru
U33. These are the 256K ram-chips. You can solder them to
the mother board, or use sockets. Now take a piece of wire
approx 12 in. long and run a jumper from pin one on each of
the 256K ram-chips to the next. After you do this the wire
will be connected to pin 1 on Z2 thru Z9 and you should have
about 6 inches left over.
Next, desolder and remove U23 (CO14795), and replace it
with a 40 pin socket. Bend up pins 15 and 16 on U23 and
insert it in the socket you just installed. Take Z1
(74LS158) and bend up all the pins on it except pins 8 and
16. Put this "piggy-back" on top of U20 (HD14050) and
solder pins 8 and 16 of Z1 to pins 8 and 16 on U20. Now
solder a short jumper from pin 15 on Z1 to pin 8 of Z1.
Now, find chip CO21697 (40 pin ), find its pin 21.
Just to the lower right of pin 21 is a solder pad on the PC
board (see diagram 1 for exact location). Solder a wire to
the pad and run it to pin 1 on Z1.
Next solder a wire to pin 15 (one of the two you bent
out) of U23 and connect the other end to pin 2 on Z1.
Solder a wire to pin 16 on U23 and connect the other end to
pin 3 on Z1.
Take R1 (33 ohm) and trim the leads to about 1/4 in.
Take the wire you connected to pin one on the 256K ram-chips
and solder it to one end of R1, solder the other end of R1
to pin 4 on Z1. Re-assemble the RF shield and case and you
are finished.
PARTS LIST
Quantity Part Id Description
1 Z1 74LS158 (2 to 1 Multiplexer)
8 Z2-Z9 41256 dynamic RAM (150ns)
1 R1 33 ohm 1/4 watt resistor
1 40 pin socket
8 16 pin sockets (optional)
The next page is a quick overview of the bit table and
numbers to be used in location 54017 (PORTB). I have
finished modifying a ramdisk handler for the extra ram. It
uses a ram based OS so basic XE or XL can't be used. At
present the best deal for this mod. is to use MYDOS 4.0.
This supports a very large single density ramdisk. With
basic XE you can use a 1500 sector ramdisk and without it
you can have about 2000 sectors.
This upgrade has been built and tested on a BBS, it has
run for days on end without a memory loss or error. If you
need help or more information feel free to call the Peanut
Gallery (408)-384-3906. 24HR, 300/1200 Baud. Leave mail to
the Sysop(thats me). Good luck and let me know if you write
a better handler.
Memory Control Register 54017 ($D301)
Bit 7 6 5 4 3 2 1 0
D a b C c d B R
D=0 enable diagnostic ROM.
B=0 enable BASIC ROM.
R=1 enable OS ROM.
C=0 enable extended RAM.
abcd= memory control bits.
--------------------
Bank # Control #
--------------------
Bank 0 -------->131|
Bank 1 -------->135|
Bank 2 -------->139|
Bank 3 -------->143|
Bank 4 -------->163| Basic= off
Bank 5 -------->167| OS = on
Bank 6 -------->171| ENH = on
Bank 7 -------->175|
Bank 8 -------->195|
Bank 9 -------->199|
Bank 10 ------->203|
Bank 11 ------->207|
Bank 12 ------->227|<--\
Bank 13 ------->231| \
Bank 14 ------->235| / 130XE Banks
Bank 15 ------->239|<--/
--------------------
If you are using MYDOS 3.016 and wish to use Basic XE
and a ram-disk at the same time, boot DOS and poke 5275,163
and 5324,16. Go to DOS and write the new DOS. This will
keep the two from "bumping" into each other. A similar poke
can be done to DOS 2.5, it is poke 4838,163. The handler I
have will set up 192K of the extra ram as 2 SD ramdisks or 1
DD ramdisk.
If you are a hot-shot programmer (I'm not) I think a
print spooler that uses part of this ram would also be very
nice. This mod is easy to do and perfect for running a BBS.
One note, on compuserve there is a mod by Rich Andrews which
should not be confused with this one, his uses 33 new chips
and mine uses 9 new chips. Have fun.
Scott Peterson
Diagram #1:
25-24-23-22-21
: X <-- solder here.
C021697 : *
: *
16-17-18-19-20 *
Also, ICD has a RAMdisk handler available on their BBS
(815-968-2229) that will support this upgrade.