Macintosh II supporting more than 8MB of RAM issues

jasa1063

New Tinkerer
May 30, 2022
40
24
8
I just acquired a Macintosh II. Installing 8x4M 30-pin SIMMs, I get a black screen and a sad mac tone. 8x1MB 30-pin SIMMs work just fine. It does have the FDHD upgrade but, still has the Apple AMMU installed. The ROM version is $0178 according to the info screen in SpeedOMeter. So is this a ROM issue or does it require a MC68851 PMMU to work with more than 8MB of RAM or could it be something else I am missing? I already posted a request for a MC68851 PMMU. Any help would be appreciated.
 

jasa1063

New Tinkerer
May 30, 2022
40
24
8
I found out you need PAL SIMMs if you want to use more than 8MB of ram on the Macintosh II. There are some on Garrett's Workshop on Tindie, but are currently out of stock.