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
UUCP
or
cu(C)
over a modem connection at high line speeds.
Examples are:
-
incoming characters are lost intermittently
-
UUCP generates unkillable uucico processes
-
cu stops executing and will not exit
-
an intermittent ``double echo'' is seen
These problems rarely show up when a serial port is used with
a terminal.
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.
NOTE:
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'').
Next topic:
About parallel ports
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Serial port speeds, line-mode labels, and UART limitations
© 2005 The SCO Group, Inc. All rights reserved.
SCO OpenServer Release 6.0.0 -- 03 June 2005