The final step, the 1088XE
By Scott Peterson, April 1986
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Well, this is it for me, the last installment on the 130XE. I have not built
this mother, but the theory behind it has been built and tested. This doc
assumes you have already built and tested a 576K 130XE. To finish it you will
need the following
Parts:
Quantity Part No. Description.
--------------------------------
16 41256-15 256K DRAM'S
1 7432 Quad OR gate
1 7404 Quad invert
buff.
2 33 ohm Resistors
Small piece of PC board.
--------------------------------
Note: On the 74 series, you can sub them with 74LS series chips, they use
less power.
Tools:
Nothing fancy, a fine tip soldering Iron and some fine wire,etc.
DISCLAIMER:
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
CAREFUL!!
Mount the 7404 and the 7432 on a small PC board (1in. X 2in.). Connect
together pin 14 on the 7432 and pin 14 on the 7404 with a length of fine
wire. This is the +5v supply to the chips, connect it to pin 14 of any 14
pin chip in the 130XE or pin 16 of any 16 pin chip in the 130XE. Next connect
a length of wire to pin 7 of the 7432 and pin 7 of the 7404. This is ground
for the two chips, connect it to pin 7 of any 14 pin chip in the 130XE or pin
8 of and 16 pin chip. Next, take U23 out of the socket and bend up pin 17,
reinsert it in the socket. Solder a piece of wire to pin 17 of U23, and
connect it to the 7432 pins 2 and 5. Next connect a wire to pin 14 on
U23(PIA) run it to pin 1 on the 7404 and pin 1 on the 7432. Now connect a
wire from the 7432 pin 6 to pin 17 of the socket U23 is in. Find the 74LS138
you piggy backed to the mother board when doing the 576k mod. Remove the
jumper from pins 1 and 16. Solder a wire from pin 3 of the 7432 on the PC
board to pin 1 of the piggybacked 74LS138. Put some double backed tape on
the PC board and stick it somewhereon the mother board of the 130XE. RAM-CHIP
installation(lots of them!) Take the 16 new ramchips and cut pin 15 on all of
them in half so only the 'fat' part is left. Now, you have to piggy back them
on-top of the 64K drams(the left-most row of chips). Solder in 8 of them,
connecting all pins except pin 15, then connect a jumper to pin 15 of each
new ram chip. Make sure you have about a foot left over. Solder in the next
8 doing the same thing. When you get done you should have 2 new rows of 256k
DRAM's soldered in on-top of the 64K DRAM's, with a 2 wires, one connected to
all pin 15's of the middle row and another connected to all the pin 15's of
the top row. Take one wire and go out a few inches and install a 33 ohm
resistor in-line, cover with heat shrink tubing and do the same to the other
wire. Connect one wire to pin 15 of the 74LS138 and the other to pin 13 of
the 74ls138.
Your done!!! Sorry, as of right now I know of no software to run on this. I
release this doc file with out testing it. I have built the small circuit on
the PC board and connected it in a 576K 130XE and used it to move the memory
instead of the basic control bit, so I know it works, this little circuit
works in both the 800XL or 130XE if you have something you would like to use
bit 7 (self test bit) for. If you have constructed a 320XE mod and would
like to use bit 7 instead of bit 5, this is a good way to do it. A warning
though, you will regain your antic enhanced mode but software written for
the original 320XE mod will not run on it after you do it. If you are trying
to figure out your memory control bits here's a cheat sheet.
Decimal 128 64 32 16 8 4 2 1
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Control bit 7 6 5 4 3 2 1 0
---------------------
Just find you control bits and add them up to figure out the decimal control
number. When you get done you should have in one switch position a 130XE
with 320K,built in basic and antic enhanced mode. In the other position you
lose antic enhanced mode, internal basic but you have 1088K of memory, 64
banks of 16K. By the way, typing BYE will still throw you into the self test
mode (bit 7 still works).
Good Luck
SCOTT PETERSON