PLIP uses several different data transfer methods. The first (and the
only one implemented in the early version of the code) uses a standard
printer "null" cable to transfers data four bits at a time using
data bit outputs connected to status bit inputs.
The second data transfer method relies on both machines having
bi-directional parallel ports, rather than output-only ``printer''
ports. This allows byte-wide transfers and avoids reconstructing
nibbles into bytes, leading to much faster transfers.
Subsections