Memory Map
| Start Address | End Address | Description |
|---|---|---|
| FF 0000 | FF FFFF | Auto-vector Read, VPA |
| FE 0000 | FE FFFF | Normal/Idle Mode, Test |
| FD 0000 | FD FFFF | SCC |
| FC 0000 | FC FFFF | Slot Configure |
| FB 0000 | FB FFFF | Sound |
| FA 0000 | FA FFFF | Video |
| F9 0000 | F9 FFFF | SCSI |
| F8 0000 | F8 FFFF | ROM Diagnostics |
| F7 0000 | F7 FFFF | VIA |
| F6 0000 | F6 FFFF | SWIM |
| F0 0000 | F5 FFFF | Reserved (Unknown) |
| E0 0000 | EF FFFF | PDS ROM |
| A0 0000 | DF FFFF | Expansion ROM |
| 90 0000 | 9F FFFF | Permanent ROM |
| 10 0000 | 8F FFFF | Expansion RAM |
| 00 0000 | 0F FFFF | Permanent RAM |
Permanent RAM
Address Space: 0x000000-0x0FFFFF
Size: 1MB (0x100000)
Address Lines When Selected:
| A23 | A22 | A21 | A20 | A19-A0 |
|---|---|---|---|---|
| L | L | L | L | x |
Permanent RAM Layout (M5120):
| 1 | 2 | 3 | 4 | |
|---|---|---|---|---|
| B | 0x000000 - 0x00FFFF | 0x010000 - 0x01FFFF | 0x020000 - 0x02FFFF | 0x030000 - 0x03FFFF |
| C | 0x040000 - 0x04FFFF | 0x050000 - 0x05FFFF | 0x060000 - 0x06FFFF | 0x070000 - 0x07FFFF |
| D | 0x080000 - 0x08FFFF | 0x090000 - 0x09FFFF | 0x0A0000 - 0x0AFFFF | 0x0B0000 - 0x0BFFFF |
| E | 0x0C0000 - 0x0CFFFF | 0x0D0000 - 0x0DFFFF | 0x0E0000 - 0x0EFFFF | 0x0F0000 - 0x0FFFFF |
| F | 0x000000 - 0x00FFFF | 0x010000 - 0x01FFFF | 0x020000 - 0x02FFFF | 0x030000 - 0x03FFFF |
| G | 0x040000 - 0x04FFFF | 0x050000 - 0x05FFFF | 0x060000 - 0x06FFFF | 0x070000 - 0x07FFFF |
| H | 0x080000 - 0x08FFFF | 0x090000 - 0x09FFFF | 0x0A0000 - 0x0AFFFF | 0x0B0000 - 0x0BFFFF |
| J | 0x0C0000 - 0x0CFFFF | 0x0D0000 - 0x0DFFFF | 0x0E0000 - 0x0EFFFF | 0x0F0000 - 0x0FFFFF |
Expansion RAM
Space allocated for up to 8MB of expansion RAM.
Address Space: 0x100000-0x8FFFFF
Size: 8MB (0x800000)
Permanent ROM
Address Space: 0x900000-0x9FFFFF
Size: 1MB (0x100000)
The stock ROM is 256KB repeated in a 1MB address space.1
The permanent ROM can be disabled and replaced with external ROM by flipping a DIP switch on the M5120 or removing a jumper on the M5126.
Address Lines:
| A23 | A22 | A21 | A20 | A19-A0 |
|---|---|---|---|---|
| H | L | L | H | x |
Expansion ROM
This 4MB of address space is reserved for ROM expansion.
Address Space: 0xA00000-0xDFFFFF
Size: 4MB
PDS ROM
Address Space: 0xE00000-0xEFFFFF
Size: 1MB
Reserved (Unknown)
Address Space: 0xF00000-0xF5FFFF
See Also:
Slim Card Registers
SWIM
Address Space: 0xF60000-0xF6FFFF
Size: 64KB
VIA
Address Space: 0xF70000-0xF7FFFF
Size: 64KB
ROM Diagnostics
Address Space: 0xF80000-0xF8FFFF
Size: 64KB
The system checks for diagnostic ROMs at this location.
SCSI
Address Space: 0xF90000-0xF9FFFF
Size: 64KB
Video
Address Space: 0xFA0000-0xFAFFFF
Size: 64KB
Sound
Address Space: 0xFB0000-0xFBFFFF
Size: 64KB
Slot Configure
Address Space: 0xFC0000-0xFCFFFF
Size: 64KB
See Also:
CPU GLU
SCC
Address Space: 0xFD0000-0xFDFFFF
Size: 64KB
Normal/Idle Mode, Test
Address Space: 0xFE0000-0xFEFFFF
Size: 64KB
See Also:
Idle Speed Register
Auto-vector Read, VPA
Address Space: 0xFF0000-0xFFFFFF
Size: 64KB
-
The ROM is selected in a 1MB range, however it is only a 256KB ROM and only has 256KB of address lines connected, so the ROM will be repeated across the 1MB space. ↩