Troubleshooting serial cards
Older computers or add-on serial I/O cards use the slower
8250 or 16450 UARTs to control their serial ports.
Some revisions of the 8250A chip do not handle interrupts properly and
should not be used with SCO OpenServer systems.
Problems with slow UARTs can show up when using
over a modem connection at high line speeds.
These problems rarely show up when a serial port is used with
They are more often associated with high-speed serial input over
a modem link.
Avoid connecting high-speed modems to ports that are controlled by
slow serial control hardware such as 8250 or 16450 UARTs.
incoming characters are lost intermittently
UUCP generates unkillable uucico processes
cu stops executing and will not exit
an intermittent ``double echo'' is seen
We strongly recommend that you use 16550 (or better) UARTs
on serial ports that are connected to high-speed modems.
The 16550 has a 16-byte receive buffer that allows
it to operate reliably at much higher speeds than
the 8250 and 16450 (see
``Serial port speeds, line-mode labels, and UART limitations'').
``Serial device resources''
for information about how to monitor and tune the performance of
dumb serial ports.
About parallel ports
PCI serial card ports and baud rates
© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003