As long as I'm investigating interchangeable parts on a Mac Plus, has anyone tried putting 64K ROMs in the Mac Plus?

Also, the Mac Plus (and the SE for that matter) can be reduced to 512K RAM, basically turning it into a 512Ke with SCSI, by using two 256K SIMMs in one row only. Are there such things as 128K SIMMs to explore a 256K Macintosh, as I've heard was a consideration at one point in the original Macintosh development? I guess 64K SIMMs to emulate a 128K as well would be pushing it, eh?

Click to expand...

There aren't any such things as 128K SIMMS. Because of the multiplexed address bus of DRAMs, adding one more address pin actually quadruples the address space. So, DRAM chip capacities grow by 4x. 64kbit chips were followed by 256kbit, etc. Making a 128K simm would be possible, but it would be an unnatural act requiring additional logic.

And I have put 64K roms in a Plus board, by accident. Didn't do much testing that way, as I changed things back as soon as I figured out my error. No smoke, though. The Plus powered on fine, but I don't remember much else.