Editing Macintosh II (section)

=== Memory Architecture ===
The Macintosh II featured a sophisticated memory subsystem that represented a major departure from earlier Macintosh designs. The system utilized 30-pin SIMM (Single In-line Memory Module) slots, with eight slots available for memory expansion. The memory controller supported both 256 KB and 1 MB SIMMs, though these could not be mixed within the same bank.<ref>{{cite book |last=Kobler |first=Randy |title=The Macintosh II Repair and Upgrade Secrets |year=1990 |publisher=Hayden Books |isbn=0-672-48452-8 |pages=145-167}}</ref>

Memory was organized in two banks of four SIMMs each, labeled Bank A and Bank B. The system required that SIMMs be installed in complete banks of four modules, and both banks had to contain the same capacity SIMMs. This configuration allowed for memory capacities of:
* 1 MB (four 256 KB SIMMs in Bank A)
* 2 MB (eight 256 KB SIMMs in both banks)
* 4 MB (four 1 MB SIMMs in Bank A)
* 8 MB (eight 1 MB SIMMs in both banks)

Later, with the introduction of 4 MB SIMMs, the maximum memory capacity could be expanded to 68 MB using special configurations, though this required specific ROM versions and was not officially supported by Apple.<ref>{{cite web |url=http://www.lowendmac.com/ii/macintosh-ii.html |title=Macintosh II: The First Modular Mac |publisher=Low End Mac |accessdate=2023-10-15}}</ref>