| high memory | |
| address | contents |
| $EFFFFF | end of VIA space |
| $E80000 | beginning of VIA space |
| $DFFFFF | end of IWM space |
| $D00000 | beginning of IWM space |
| $BFFFFF | end of SCC write |
| $B00000 | beginning of SCC write |
| $9FFFFF | end of SCC read |
| $900000 | beginning of SCC read |
| $5FFFFF | end of SCSI |
| $580000 | beginning of SCSI |
| $41FFFF | end of ROM |
| $400000 | beginning of ROM |
| $3FFFFF | end of RAM for 4MB Mac Plus |
| $27FFFF | end of RAM for 2.5MB Mac Plus |
| $1FFFFF | end of RAM for 2MB Mac Plus |
| $0FFFFF | end of RAM for 1MB Mac Plus |
| varies | sound buffer |
| varies | System Error Handler area |
| varies | main screen (ScrnBase) |
| varies | MacsBugs (optional) |
| varies | RAM cache (optional) |
| varies | Jump Table (A5 relative) |
| varies | application and QuickDraw globals (A5 relative) |
| varies | stack (A7) |
| varies | Application Heap (ApplZone) |
| $001600 | beginning of System Heap (SysZone) |
| $000E00 | beginning of Toolbox A-trap table |
| $000800 | additional low-memory global area |
| $000400 | beginning of OS A-trap table |
| $000100 | beginning of low-memory global area |
| $000000 | beginning of RAM Motorola 680x0 vectors |
| low memory | |