TOPIC -------------------------------------------------------
Are there any differences between the two built-in serial ports on
Macintosh computers?
DISCUSSION --------------------------------------------------
The two built-in serial ports on Macintosh products are nearly identical,
except for the differences detailed in this article. Here are the
differences:
Ñ╩Port A (the modem port) has a higher interrupt priority; it is more
suitable for high-speed transmission.
Ordinarily, Port B (the printer port) should be used for output-only
connections, or at low baud rates; the Port A (the modem port) has no
such restrictions. Whenever interrupts are turned off for longer than
100 microseconds, the Serial Driver stores any data received through Port
A (the modem port,) and later passes the data to the modem port's input
driver.
Note: For more information, see "Inside Macintosh Volume 2."
Ñ╩Port A on the Macintosh SE and Port A on the Macintosh II support
synchronous transmission, but Port B does not. Earlier Macintosh products
do not support synchronous transmission through either port.