The upgrade itself requires good desoldering/soldering skills, because there is a lot of desoldering/soldering in this upgrade. But, as we're all retro nuts, this shouldn't be a problem, I guess.
So, let's get crackin'.. Ok, what do we need for this upgrade:
- 8x 41256 DRAM's
- 8x DIL-16 turned pin sockets
- 1x DIL-40 turned pin socket
- 1x 74LS158 (or 74HC158)
- 1x 33 Ohm resistor
- Some jumper wire
- Soldering Iron
- A lot of patience
My 130XE board, before the upgrade:
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The little PCB in the middle is the Sophia RGB upgrade
On my 130XE, there are two memory banks of 64KB in 16x 4264 DRAM's (rubbish, but as long as they work...) making up 128 KB of RAM. Now, start with desoldering the DRAM chips on the right side of the board. Do this carefully, because Atari used some cheap ass PCB's for the 130XE, so tracks/traces can lift quite easily.
If all the DRAM's have been removed, solder in the DIL-16 sockets, turn over the board and connect all of the pin 1's on the RAM sockets together with jump wires and feed enough wire through the left hole in the board (see image).
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All of the pin 1's tied together
Now desolder the 6520 chip and remove it carefully from the board and solder the DIL-40 pin socket in it's place. Bend up pins 15 and 16 of the 6520 chip and insert it in the socket.
Take the 74LS158 chip, bend up all of the pins, except pins 8 & 16. To prevent shorts I recommend shortening the pins of the 74LS158, except of course pins 8 & 16, because we'll need them. Now, place the 74LS158 on top the CD4050 chip and solder pins 8 & 16 to pins 8 & 16 of the CD4050 chip.
Take some short wire and connect pin 15 to pin 8 of the 74LS158;
Take another wire and connect pin 1 of the 74LS158 to pin 30 on the GTIA chip;
Connect using some wire pin 15 of the 6520 chip to pin 2 of the 74LS158 chip;
Now connect pin 16 of the 6520 chip to pin 3 of the 74LS158 chip;
Take the 33 Ohm resistor, solder it to pin 4 of the 74LS158 chip, connect the wire from the RAM sockets we soldered earlier to the other end of the resistor. I recommend some heat shrinking tubing for insulation to prevent shorts.
Insert the 41254 DRAM chips in the sockets.
The end result should look like this:
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320 KB RAM upgrade in place
We're almost finished now, as stated earlier this upgrade disables ANTIC banking. Fortunately, this can be fixed by joining the solder pads of pins 15 and 16 of the 6520 chip together. Turn over the board and make a solder bridge between pins 15 and 16. This fixes ANTIC banking.
Now, place the board with some insulation on a table, connect all the needed stuff and turn it on. It should come up with the familiar black/blue screen with the READY prompt. If it doesn't, check for shorts or lifted traces or the soldering for cold joints.
Now, reassemble everything and enjoy your 320 KB 130XE
To test the 320 KB upgrade try the NUMEN demo. If it runs, you know your 320 KB upgrade works!
I know homesoft have games that can use that 320K!
