SIMM to ZIP adapter

Copyright and Distribution

This project is freeware, even because I invented nothing. You can send me whatever you want, just to tell me if you liked it or not.

History

All the A3000 owners know how hard to find and expensive are 1Mbx4 ZIP chips. For a long time I tried to discover a way to build a board to "emulate" a 1Mbx4 ZIP chip using my old 256Kbx4 ZIP chips; I made many projects but none had success. After spending many money to buy 8 MB of these chips, I started to become smarter ( ? :). If ZIP chips are so expensive, why don't use 1Mbx4 chip in some other package ? Then I started to visit all the electronic shops and I asked for DRAMs in any package, but I discovered that no one sells 1Mbx4 chips. One day, giving a envy look to a very cheap 4 Mb SIMM, I noted that the chips it used are the famous 1Mbx4 chips !!!! After collecting all the needed informations I started to project and build this adapter.

Limits

I made this adapter for my SCSI controller, which uses a very strange method to manage its memory expansion (there is only one /RAS for all the chips, and the memory banks are selected through the /WE signal instead of the /CAS signal).
The first version of my adapter works also in the A3000 ! My friend Andrea was crazy enough to try it in his A3000, so you can ask him directly
The second revision is a rework of the adapter I build for my SCSI controller; probably also this can be used in the A3000 if NO MODIFICATION are made on the SIMM and without the extra /WE connection.

Theoric realization

[1]= U850   On the A3000 it's         [1]= M16    On my SCSI controller
[2]= U851   the first 4 MB 32 bit     [2]= M12    they are 2 banks
[3]= U852   memory bank               [3]= M8     2 MB 16 bit each
[4]= U853                             [4]= M4
[5]= U854                             [5]= M15
[6]= U855   see the pics              [6]= M11    see the pics
[7]= U856                             [7]= M7
[8]= U857                             [8]= M3
    

The SIMM data lines are connected, in groups of 4, to only one chip on the SIMM. The addres lines are common to all the chips on the SIMM. The /OE signal of all the chips on the SIMM is connected to GND.

Practical realization

It was impossible to me to found sockets for the SIMM so I soldered wires directly on the SIMM and I connected them to the ZIP sockets.
CHECK EVERYTIME IF THE CONNECTION ARE NOT FAULTY AND THERE ARE NO SHORT CIRCUITS !!!

Credits, thanks and greetings go to:

My brother Leonardo, for his insistence which push me to conceive and realize this project, and his hands, very useful when soldering.

Dr. Segio Congiu, my Electronic Computers professor, who made me understand what I was doing.

Frank de Wit and Frank (Falstaff, author of the GIICM) for their help

The people of the technical support team at Motorola, in particular Bill Gorman, for their answers to my "exotic" questions.

Greetings to:

The Amiga community of the Padova University, the worldwide Amiga community, the Amiga Report staff, the Amiga Technologies team, and everyone who knows me.

Back to index