This approach is called ‘Programmed Input/Output’, or PIO, and was used extensively into the early 1990s for for example PATA storage devices, including ATA-1, ATA-2 and CompactFlash.

the spec referred to the drives as device 0 and device 1, despite master/slave being more commonly recognized. When installing two PATA drives, jumpers on the back of the drives let you designate ...