Memory Mapping Mode
From SpecNext official Wiki
| Number | $8F |
|---|---|
| Readable | Yes |
| Writable | Yes |
| Short Description | Select memory mapping mode |
bits 7:2 = Reserved, must be zero bits 1:0 = Mapping mode applied (hard reset = 0) 00 = Standard ZX 128k +3 01 = Reserved 10 = Pentagon 512K 11 = Pentagon 1024K (limited to 768K on 1MB machines)
* Standard ZX 128K +3 = principally ports 0x7ffd, 0xdffd, 0x1ffd * Pentagon 512K = principally port 0x7ffd * Pentagon 1024K = principally ports 0x7ffd, 0xeff7 ** The mapping modes affect how ports 0x7ffd, 0xdffd, 0x1ffd and 0xeff7 carry out memory paging, see ports.txt