| reg | value | descr |
|---|---|---|
| AH | 0xc0 |
| reg | descr |
|---|---|
| AH | set, 80h for PC & PCjr, 86h for XT (BIOS after 11/8/82) and AT (BIOS after 1/10/84) |
| ES:BX | pointer to system descriptor table in ROM of the format (see below) |
| offset | size | description |
|---|---|---|
| 00h | word | length of descriptor (8 minimum) |
| 02h | byte | model byte (same as F000:FFFE, not reliable) |
| 03h | byte | secondary model byte |
| 04h | byte | BIOS revision level (zero based) |
| 05h | byte | feature information, see below |
| 06h | dword | reserved |
see Machine ID