| Port | Read | Write |
| #7Fxx | N/A | Standard RAM Expansion (512K) |
| #DFxx | N/A | Upper ROM Bank |
| #FD00-#FD05 | ? | ? |
| #FD06 | IDE Alternate Status | IDE Digital Output |
| #FD07 | IDE Drive Address | N/A |
| #FD08 | IDE Data Register | IDE Data Register |
| #FD09 | IDE Error Register | IDE Features Register (Write Precomp Reg.) |
| #FD0A | IDE Sector Count | IDE Sector Count |
| #FD0B | IDE Sector Number | IDE Sector Number |
| #FD0C | IDE Cylinder Low | IDE Cylinder Low |
| #FD0D | IDE Cylinder High | IDE Cylinder High |
| #FD0E | IDE Device/Head Register | IDE Device/Head Register |
| #FD0F | IDE Status Register | IDE Command Register |
| #FD10 | PS/2 Mouse Status | N/A |
| #FD11 | ROM Enable SYMBiFACE II Roms | ROM Disable SYMBiFACE II Roms |
| #FD12-#FD13 | ? | ? |
| #FD14 | RTC Data | RTC Data |
| #FD15 | N/A | RTC Index |
| #FD16 | ? | ? |
| #FD17 | Map upper ROM to 4000h-7FFFh (for writing to ROMs) |
Don't map Upper ROM to 4000h-7FFFh (default) |
| #FD18 | PS/2 Mouse Status | N/A |
| #FD19-#FD3F | ? | ? |