Because the speed of the Macintosh computer's CPU affects the printing
time, printing from a Macintosh Plus to the Personal LaserWriter LS is
slower than from a higher-speed computer, like the Macintosh Classic II
or Macintosh IIci.
The Personal LaserWriter LS has a high-speed RS-422 serial interface,
externally clocked at 909KB/sec. At optimum performance, it prints four
pages per minute.