As anyone who has an Atari 600XL knows it only came with 16k. Good enough to run game cartridges but nothing else. Atari's solution was this little device that attached to the BUS adapter on the back. the Atari 1064.
These are rather impossible to get a hold of these days (in fact I had a hard time just finding a picture) so the current procedure to up the memory is adding the memory internally.
There are several ways of doing this, lotharek.pl/ has a nifty little chip that just installs under the 6502. Easy and not all that expensive (except the shipping). Another way which is harder is to install the 64k chips and slightly modify the motherboard. No easy here. Bending up pins off chips and soldering wires to them. The pathway of the true geek (who doesn't have much money as this cost only $7.00 shipped).
Legal: I am not a professional but have had years of experience with computers. Still, use these instructions at your own peril. I assume no responsibility.
Put on a stax of wax (or MP3 player) with your favorite music. Mine is Episodes 1-6 of Star Wars by John Williams. I made it to Episode 3 before I had finished.
Step 2.) Everything else.
My tools; screwdriver, needle nose pliers, chip puller, small wire cutters, wire stripper, helping hand and solder station.
My pile of notes and pictures:
Now the Atari 600XL has 4 bolts holding the back cover along the edges. unscrew these and gentle remove the top since the top is attached to the motherboard via the, very delicate, keyboard cable.
If you still have the metal shielding over the motherboard remove it via the bolts along the edge. I had previously removed mine and stored it. I, personally, find no reason to have it on the motherboard but it's up to you if you want to return the shield after the installation.
Now disconnect the keyboard ribbon cable. The keyboard cable is attached to an edge card that is slotted into the motherboard. GENTLY rock the edge card out of the socket pulling on the edge card NOT THE RIBBON till the edge card comes loose.
On to the main attraction, the motherboard and the chips.
First is to remove the 2 x 16k chips and replace with the 2 new 64k chips. Chip location is U12 and U11. The location is noted on my note of the chip locations.
NOTE: use a chip puller to keep from damaging the chips or the socket in removal. Here is a picture of one of the 16k chips is still in the clutches of the puller.
Below is my map of the motherboard. I have marked the location of the chips on the map. See where the RAM chips are that need to be replaced.
And another note: I got lucky in that all my chips were socket-ed. Yours may not in which case you will have to de-solder each chip. Unless you are a pro I would go with lotharek.pl/ solution (mentioned above) which is much easier. Desoldering a chip, unless you know what you are doing, always runs the risk of frying it.
Now you can test the 600XL. The memory will still show as 16k (if you hook up the keyboard which I didn't) as you haven't setup the matrix yet. But you will be able to see if maybe you have a bad chip before you go further.
Now comes the time that tries men's souls, pulling the support chips and soldering wires on the legs. The below map shows the location of the chips to pull and the wires to solder.
I started with pulling up U5. This chip you bend up pin 3 (see mark) and solder on a wire to it.
First thing is to prepare the wire by brazing the end and putting the shrink wrap on. below picture.
This and next picture you see where I bent up pin 3 that I had pre-marked on the chip before pulling the chip. I pre-marked the pins on all the chips before I pulled them so that I would have no confusion of which pin is which compared to the picture. Also note the slight kink bend I put in the chip leg. this is to ensure the leg, which is much too long, doesn't accidentally touch the other chip when installed. I also cleaned the leg with alcohol to be sure to get a good solder.
This is after I soldered on the wire and wrapped the leg in shrink wrap. When soldering the leg be sure to work as fast as possible. Too much heat on the chip can fry it. If you have a problem soldering on the wire take a break and let the chip cool before you try again. Oh, I forgot to take a picture of this but I held the chip with in the jaws of the helping hand to steady the solder.
Next, carefully, reinsert the chip back into the socket. be sure all pins are in the slot except the one that is bent with the wire attached. Here is U5 and U6 both done.
On U6 you bend up pin 10 and attach the wire just like the previous one.
Now solder the two wires to the motherboard. U5 goes to the leftmost-C location (see above map) and U6 goes to the rightmost-J location. I just put a dot of solder on the spots then soldered on the wires into that dot. be careful NOT to let the solder bleed over into the other solder point or on one the traces on the board.
on to the next and final chip mod modding the chip U16 pin8 (above picture. finished product, yes getting ahead of myself but picture of step went bad). Same as the other two, bend out straight. I this case no need for kink.
Now the wire from U16 goes to resistor R36. Clip or un-solder the one end of the resistor. This is the end you solder/attach to the wire from U16. I clipped the resistor in the the below picture then bent it straight and soldered the wire to it (again see above picture of finished process). This is a picture of the resistor that U16 is being soldered to.
Now it's ready to close up and test. Attach the keyboard back by putting the slotted connector back into it's slot, gently. Close up the 600XL and screw back in the 4 screws. Attach a power a sully and monitor cable and run ?FRE(0) which should now show 37902 and run the built in memory self test.
You are all done. Rejoice and be glad as your 600XL now has as much memory as it's snotty big brother the 800XL. That is, if you didn't screw anything up.