ROMSIMM for Macintosh SE/30

[Koolstar42]

I am the proud owner of a Macintosh SE/30 and I wanted to experiment with a 32bit 'clean' ROM. So I decided to design my own pcb. After some soldering woes I got it to work, but as per usual, I now have about 25 SIMM boards left over. (3 SIMMs fit on a 10x10 board. Wink

If somebody is interested, they are available for 50 cents per SIMM (plus $3 for shipping). You can cut them yourself if you want.

One word of warning.... I used SMD PLCC32 sockets, which are a pain to solder without special tools. I ended up using the 'hot plate' soldering method, which worked surprisingly well. I intend to just solder the flash ROMS (AM29F010B) directly to the board when I'm done for the final product.

I also made gerbers for a TH version from the same design (untested). If you like those, you can order then yourself (use 1.2 mm board) - 1 TH plus 2 SMD SIMMs per board.

 

[glitch]

Nice! Good to see an open version of this, I believe someone else has made a rather expensive closed-source version.

 

[olePigeon]

DougG3 over at 68k MLA made the original, first programmable ROM SIMM. Then BMOW took over that project for him, so he sells that one. Then GG Labs made their own version. I like seeing new homebrew hardware. It's awesome.

 

[GiGaBiTe]

PLCC sockets aren't difficult to solder, you can use a hot air tool at 250C to get them soldered on the board without melting the socket.

 

[Koolstar42]

Thanks for the tip. I did not have a hot air tool, now I do. Ill give it a try

 

[olePigeon]

@Koolstar42 You should see if your SIMM is programmable using the ROM-inator II programming board:

http://www.bigmessowires.com/mac-rom-inator-ii-programming/

Incidentally, the GG Labs one works with it. I'm willing to bet yours does, too, if your ROM simm is working as intended.

Edit: Oh, nuts. He no longer sells them. But he does offer the schematics and code for free so you can build one.

https://github.com/dougg3/mac-rom-simm-programmer.cad/tree/master/programmer

The reason it's useful is so you don't have to bother with sockets on the SIMM itself.

 

[Koolstar42]

I'm pretty sure that does not work, as I wired #WE to VCC to keep routing as lean as possible. I just program the ROMs separately. It is a one time only affair, so making the SIM programmable requires building extra kit which will be used only once. I just used sockets for prototype and testing purposes. My final board will omit the sockets altogether. I will solder the programmed chips directly to the SIMM when I get to it.

One useful aspect of this ROM is that it you can boot from it. Very useful if something happens to the drives, which is totally not unthinkable.

Another issue that gets addressed is the fact that the contacts of my original SIMM are quite worn, causing issues. The new SIMM is only HASL, but it works a lot better.