Geneve physical memory map
The physical memory map declares which physical addresses are used to access memory regions or devices.
Native mode
Memory map
| Address | Banks | Region | |
|---|---|---|---|
| 000000 | 00-3F | 512 KiB On-board DRAM | Slow RAM (1 ws) |
| 080000 | 40-7F | 512 KiB On-board DRAM expansion | Allocated, but technically infeasible (no sockets or signal lines) |
| 100000 | 80-B7 | 448 KiB P-Box space | May be used my MEMEX card |
| 170000 | B8-BF | 64 KiB P-Box space | Used by current expansion cards |
| 180000 | C0-E7 | Future expansion | SRAM expansion in the P-Box |
| 1D0000 | E8-EB | 32 KiB On-board SRAM expansion | Soldered on top of the existing 32 KiB chip |
| 1D8000 | EC-EF | 32 KiB On-board SRAM | Original SRAM memory (0 ws) |
| 1E0000 | F0-FF | 128 KiB Boot EPROM | Originally, only 16 KiB installed at F0,F1; mirrored |
Boot EPROM space
The Boot EPROM region may have up to 128 KiB space as 16 banks of 8 KiB. This is used with the PFM.
On reset, bank F8 is mapped into the 0000-1FFF logical address region. The EPROM on the stock Geneve defines all even banks as mirrors of F0, and all odd banks as mirrors of F1.
GPL mode
| Address | Banks | Region | |
|---|---|---|---|
| 000000 | 00-35 | 432 KiB On-board DRAM | Slow RAM (1 ws) |
| 06C000 | 36 | 8 KiB Cartridge ROM space (bank 1) | First bank of cartridge (Extended Basic style) |
| 06E000 | 37 | 8 KiB Cartridge ROM space (bank 2) | Second bank of cartridge (Extended Basic style) |
| 070000 | 38-3F | 64 KiB GRAM Cartridge space | Map byte 06 must be set to 0x03 to enable GRAM |
| 080000 | 40-7F | 512 KiB On-board DRAM expansion | Allocated, but technically infeasible (no sockets or signal lines) |
| 100000 | 80-B7 | 448 KiB P-Box space | May be used by MEMEX card |
| 170000 | B8-BF | 64 KiB P-Box space | Used by current expansion cards |
| 180000 | C0-E7 | Future expansion | SRAM expansion in the P-Box |
| 1D0000 | E8-EB | 32 KiB On-board SRAM expansion | Soldered on top of the existing 32 KiB chip |
| 1D8000 | EC-EF | 32 KiB On-board SRAM | Original SRAM memory (0 ws) |
| 1E0000 | F0-FF | 128 KiB Boot EPROM | Originally, only 16 KiB installed at F0,F1; mirrored |
Genmod
The Genmod (Geneve modification) can be run in two modes, selectable by a switch. The TI mode activates the on-board slow DRAM, which is required to run the GPL mode. The reason is that the Gate array maps the GROM accesses to the DRAM on the board, which cannot be changed to the external RAM.
TI mode
| Address | Banks | Region | |
|---|---|---|---|
| 000000 | 00-35 | 432 KiB On-board DRAM | Slow RAM (1 ws) |
| 06C000 | 36 | 8 KiB Cartridge ROM space (bank 1) | First bank of cartridge (Extended Basic style) |
| 06E000 | 37 | 8 KiB Cartridge ROM space (bank 2) | Second bank of cartridge (Extended Basic style) |
| 070000 | 38-3F | 64 KiB GRAM Cartridge space | Map byte 06 must be set to 0x03 to enable GRAM |
| 080000 | 40-EF | 1408 KiB P-Box memory expansion (MEMEX) | SRAM (0 ws) |
| 1E0000 | F0-FF | 128 KiB Boot EPROM | Originally, only 16 KiB installed at F0,F1; mirrored |
Non-TI mode
| Address | Banks | Region | |
|---|---|---|---|
| 000000 | 00-EF | 1920 P-Box memory expansion (MEMEX) | SRAM (0 ws) |
| 1E0000 | F0-FF | 128 KiB Boot EPROM | Originally, only 16 KiB installed at F0,F1; mirrored |