The MACHID byte identifies these system attributes:
- Bits 7-6: 00=II; 01=II+; 10=IIe; 11=III Emulation
- Bits 5-4: 00=Unused; 01=48K; 10=64K; 11=128K
- Bits 3-2: Reserved for future definition
- Bit 1: 1=80-column card; 0=None
- Bit 0: 1=Thunderclock or equivalent; 0=None