- The LaST Upgrade -


Last updated - March 27, 2023

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This solder-in memory upgrade will add the full 4MB RAM to a STM machine.

At the time of typing the header pins are not already soldered on the board and you need to solder them in yourself.

Firstly you need to remove your existing DRAM. I did some YouTube videos on how to remove the old RAM.

I then suggest fitting the fly lead cables next. There are four wires to solder and I suggest you solder the wires directly on the board and not with the black end connector housing as I did in the above image.The wires supplied will be random colours!

Fitting is a little bit tricky because of aligning all the pins. I would suggest firstly inserting the pins on the motherboard (without soldering initially). Then work the RAM board onto the pins. Then solder the pins on the RAM board first. then solder the motherboard pins on the bottom. Some tweezers will definitely help with assembly.

Incidentally, there is no need to remove the existing capacitors on the motherboard RAM area. I would recommend just leaving them in place as long as they are not interfering with the install.


Try to keep everything as low down and as straight as possible!


The RAM board wires are labelled MAD9,CAS1H,CAS1L,RAS1. As mentioned earlier the supplied colours of the wires are random. So I suggest simply starting with the top wire (brown in the above image) and solder that location in the first who whatever colour you like. Then soldering in the other three wires. Also as noted earlier solder the wires directly into the RAM board (without the plastic end parts). Just simply cut them off and solder the wires directly into the board.

NOTE: If you have a board revision E or later, then you may have alternative solder points as listed in the post below.

Also don't forget to check out other modifications which may be required on your motherboard on this page below!

That is pretty much it! As long as you are taking your time youshould be up and running fairly quickly. There may be some other additional information on the forum HERE.



On later motherboards there seems to be additional pads where you could solder some of the wires there is a post on the bottom of the motherboard. This may be slightly easier but it is really down to the end-user which they prefer to do.

MAD9 still require soldering on the underside of the motherboard.



C070243 REV E-I /RAS0 MOD

Revisions E and later boards have a "missing" /RAS0 resistor which can be fitted as illustrated below. These resistors help protect the DRAM from ringing /noise spikes etc. These resistors were fitted by Atari as standard on all later machines. Such as the STF/M etc. I'm not aware of any STM revisions at the time of typing which have the /RAS0 resistor fitted by default.

Revisions D and earlier boards do not even have R134 fitted. I'm afraid at the time of typing I do not currently have one of those motherboard revisions to document.

R134 is MMU pin 7 - CAS0L

R133 is MMU pin 6 - CAS0H


Carefully cut the track with a sharp scalpel or similar as illustrated above. Then carefully scrape away the green solder resist and tin the track with solder on the top half of the track.


Then solder a small resistor such as a 68R 0.125watt (1/8watt) as illustrated above.

You can of course use a more standard size resistor of 0.25watt (1/4 watt) like R134 is. Though I prefer to use physically smaller resistors when tacking them onto tracks..

For the eagle eyed people who will undoubtably get confused over the resistor value in my image. I just used a 43R resistor as it was all I had to hand at the time. Typically 68R is the preferred value but I have successfully used 33R also. So any values between 33-68R should be fine.




Assuming things when well then you can use a standard memory test program such as YAART or the older MARPET XTRA RAM test program.

If you have a diagnostic cartridge or you are unable to boot up then you can also use that. Diagnostic cartridges and serial cables are available in my web shop.