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Mac IIfx Address Space


Below is the memory map of the Input/Output of the Macintosh IIfx. Noramally, a 32 bit processor can access up to 4 gigabytes of memory, but the IIfx can only physically hold 128 megs of memory. In reality, since the IIfx the only Macintosh that uses 64 pin SIMMs, the number is far less to maybe around 64 megs.

Macintosh IIfx I/O Space*

Memory Base


 0x50040000  0x53FFFFFF  Reserved (Rep. Images)
 0x50048000  0x5003FFFF  Reserved
 0x50026000  0x50027FFF  Expansion 5
 0x50024000  0x50025FFF  Expansion 4
 0x50022000  0x50023FFF  Expansion 3
 0x50020000  0x50021FFF  Expansion 2
 0x5002E000  0x5002EFFF  Expansion 1
 0x5001C000  0x5001DFFF  Expansion 0
 0x5001A000  0x5001BFFF  OSS Local I/O
 0x50018000  0x50019FFF  BIU
 0x50016000  0x50017FFF  ADB
 0x50014000  0x50015FFF  Reserved
 0x50012000  0x50013FFF  IOP (SWIM)
 0x50010000  0x50011FFF  Sound
 0x5000E000  0x5000FFFF  Alt. SCSI (Hsk)
 0x5000C000  0x5000DFFF  Alt. SCSI (DMA)
 0x5000A000  0x5000BFFF  Alternate SCSI
 0x50008000  0x50009FFF  SCSI DMA
 0x50006000  0x50007FFF  Reserved
 0x50004000  0x50005FFF  IOP (SCC)
 0x50002000  0x50003FFF  Clock
 0x50000000  0x50001FFF  VIA

* Information gathered from Guide to Macintosh Family Hardware.