Subject: UPGRADE: 130XE -> 576K Memory (SP)

The 130XE/576K upgrade
   Scott Peterson.
Here we go again, this time I recommend you have some electronics experience
if you wish to perform the upgrade. Some of the work is duplicated from the
320K upgrade so 320XE owners will not have as much work to do. One other
point, when in the 576K mode you MUST use some sort of basic cart. as you
lose the internal basic, this is only in the 576K mode, in the 130XE mode
internal basic will function normally.
To perform this upgrade you need the following:
Low wattage fine tip soldering iron.
Vacuum de-soldering tool (like Radio Shack PN#64-2098).
Some 30-gauge wire (Radio Shack PN#278-501).
#2 phillips head screwdriver.
Heat-shrink tubing, 1/8 in. Dia.
Also a pair of small needle-nose pliers and a small flat tip screwdriver are
Z1 74LS158 
Z2-Z17 41256 (150ns.) 
Z18 74LS138 
Z19 7432 
R1-R2 33 ohm 1/4 watt resistor. 
S1 Micro-mini DPDT switch (like Radio Shack PN#275-626)
Neither this BBS or the author shall assume any liability or responsibility
for any damage real or personal for this design due to the inability to
control practices or construction techniques in building this circuit. BE
Remove the 130XE case and metal RF shield to get down to the mother board.
(320XE users go to step two).
Now de-solder and remove the eight ram chips U26 thru U33 (MT4264). They are
the row closest to the TV RF module (do NOT use solder wick, the circuit
board of the 130XE has very weak runs and they will pull loose if not
completely de-soldered). Replace these with the 16 pin low profile sockets.
Take a piece of wire approx 12 in. long and run a jumper from pin 1 of each
socket to the next. When you are done the wire should be attached to pin 1 of
each of the new sockets and you should have about 6 inches left over. Do this
on the rear of the mother board and then snake the wire thru the large hole
near the ram chips.
Next, desolder and remove U23 (CO14795), and replace it with a 40 pin socket.
Bend up pins 15 and 16 and insert it in the socket you just installed. Take
Z1 (74LS158) and break off pins 5,6,7,9,10,11,12,13,14. Bend up the other
pins on it except 8 and 16. Put this "piggy back" on top of U20 (HD14050, or
4050 - located just to the right of C50) and solder pins 8 and 16 of Z1 to
pins 8 and 16 on U20. Now take a short jumper from pin 15 on Z1 to pin 8 of
Z1. Take a piece of wire about 4 in. long, solder one end to pin 30 on the
chip marked "CO14805" on the mother board, and the other end 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 1 of the ram chip sockets and solder it to one end of R1,
solder the other end of R1 to pin 4 on Z1.
Slide the mother board back into the bottom half of the plastic case (do not
use the RF shield, you must be able to get at the mother board), and attach
the keyboard. It will rest above the mother board without touching it. Test
all 41256 ram chips by putting one set of 8 in the sockets and using the
handlers (or DOS's), and then the next. After testing all ram chips remove
them all from the sockets, and take 8 of them and cut about half of pin 15
off of each one. Only the "fat" part of pin 15 should be left. After doing
this you have to "piggy back" the 8 256K ram chips with the short pin 15's
on top of the other 8 256K ram chips.
Now solder all the pins together on the stacked ram chips except for pin 15,
it should not be touching the other pin 15, make sure you have them going pin
1 to 1, pin 2 to 2,ect. When you get done you will have 8 sets of Piggy backed
256K ram chips. Now take a piece of wire about 16 in. long and run a jumper
from pin 15 to the next one on all the top 256k DRAM's, leaving about 1 inch
between each ram chip. Put these stacked ram chips into the 8 sockets you
installed earlier. Take Z18 (74LS138) and bend up all the pins except 8 and
16, cut the pins you bent up in half so only the fat part is left, and solder
pins 8 and 16 to pins 8 and 16 of the other 74LS138 right below the U23
(CO14795). Take Z19 and bend up all pins except 7 and 14, once again cut all
the pins you bent up in half and solder pins 7 and 14 to pins 7 and 14 of the
74LS08 right below U23.
Take the wire you jumpered earlier to pin 15 of Z10 thru Z17 (the upper row
of 256K ram chips) and go out 2 in. and cut the wire, now install R2 (33 ohm)
between this cut. Place a piece of heat shrink tubing over R1 and make sure
no wire is exposed and heat it with a lighter. Take the other end of this
wire and connect it to Z18 pin 14. Find the 2 33 ohm resistors just to the
right of U28 (one of the ram chips you socketized). The upper one of the 2 is
R111, desolder the right leg of it and bend it up. Take a piece of wire and
solder it to the land where you just removed the leg of R111. Connect the
other end to Z18 pin 4. Trim back the leg of R111 and solder a wire to it,
slip a piece of heat shrink tube over it and heat it up. Now connect the
other end to Z18 pin 12. Take a short wire and run a jumper from pins 1 and
16 of Z18. Take another short wire and connect a jumper from pins 3,5, and 8
of Z18. Now connect a wire from Z18 pin 2 to Z19 pin 3. Find the wire you
installed from U23 pin 15 to Z1 (74LS158) pin 2 and desolder it from U23.
Take it and reconnect it to Z19 pin 11. Ok, now pry U23 (CO14795) back out of
the socket and bend up pin 11, plug it back in. Run a jumper from pins 1 and
4 of Z19, and another jumper from pins 10 and 13 of Z19. Connect a wire from
U23 pin 11 to Z19 pin 1, and from U23 pin 15 to Z19 pin 13. Now connect a
wire from Z19 pin 8 to the right side of the 3.3K ohm resistor marked R206
(located at the bottom right of U23). Connect a wire to Z19pin 6 and run it
to pin 18 of U3 (CO61618).
Now comes the tricky part, drill a small hole (1/4 in. or so, depending on
the switch size) at the rear right on the back of your 130XE. Take the small
DPDT switch (S1) and install it in the hole. Now connect it as shown (make
sure the switch DOESN'T have a center off position);
   S1 (rear) 
   U23       ________        U23
 pin 20 ----|-O    O-|----- pin 1
            |  \  /  |
   Z19   ---|-O \/ O-|---   Z19
pins 2+12   |   /\   |    pins 5+9
            |  /  \  |
            | O    O |
Note: where the wires cross in the middle, they are NOT connected. Make the
connection from the switch to U23 on the rear of the mother board. Well
that's it(thank god). Now re-assemble the computer, being careful not to
break any wiring going to the switch. You should now have in one switch
position a 100% compatible 130xe, and in the other you have a 576K 130XE
that does not have Antic memory enhance mode and also can-not use internal
basic. In the 130XE mode you gain 64K as bit 6 of the PIA can still be used.
The following page list of the bit table and numbers to be used in location
Memory Control Register 54017(D301) 130XE in 576K mode.
Bit 7 6 5 4 3 2 1 0
    D a b C c d e R
D=0 enable diag. ROM
R=1 enable OS ROM
C=0 enable extended memory
abcde= memory control bits.
Bank#    Control#(dec)  Hex
Bank 0 ---------->129   81
Bank 1 ---------->131   83
Bank 2 ---------->133   85
Bank 3 ---------->135   87
Bank 4 ---------->137   89
Bank 5 ---------->139   8B
Bank 6 ---------->141   8D
Bank 7 ---------->143   8F
Bank 8 ---------->161   A1
Bank 9 ---------->163   A3
Bank 10 --------->165   A5
Bank 11 --------->167   A7
Bank 12 --------->169   A9
Bank 13 --------->171   AB
Bank 14 --------->173   AD
Bank 15 --------->175   AF
Bank 16 --------->193   C1
Bank 17 --------->195   C3
Bank 18 --------->197   C5
Bank 19 --------->199   C7
Bank 20 --------->201   C9
Bank 21 --------->203   CB
Bank 22 --------->205   CD
Bank 23 --------->207   CF
Bank 24 --------->225   E1
Bank 25 --------->227   E3
Bank 26 --------->229   E5
Bank 27 --------->231   E7
Bank 28 --------->233   E9
Bank 29 --------->235   EB
Bank 30 --------->237   ED
Bank 31 --------->239   EF
There is a version of MYDOS to support this mod, its called 4.1A and will run
up to 32 16K banks. At this time ICD is working on a RD.COM file to support
    Good luck

Craig Lisowski (