COM3 under XENIX 2.2.1

[Ross Oliver]

In article <2604 at auscso.UUCP> jboede at auscso.UUCP (Jon Boede) writes:
>I have an ITT AT clone running XENIX 2.2.1 ... the problem is that I can't find
>a way to make a /dev/tty3[Aa] ... I have cards with COM1 and COM2 on them
>coming out of my ears and some internal modems that work on COM3 and COM4 with
>the (ack) DOS program ProComm.  
>
>Can one make a COM3 device on an ITT under 2.2.1?  If so, what are the major/
>minor device numbers??

Some internal modem and serial card manufacturers have extended the
standard IBM COM1 and COM2 I/O addresses to create COM3, COM4, COM5, etc.
Since DOS does not use an interrupt-driven serial driver, these extra
devices work fine.  However, the XENIX serial driver is interrupt-driven,
and only two interrupt vectors are allocated to the serial driver
(IRQ4 for COM1, IRQ3 for COM2).  Therefore, unless these cards can
change their interrupt vectors as well as their I/O address, they will
not work with XENIX.  If you need more than two serial ports, you can
try one of the multiport cards, which use only one vector.  Some of
the intelligent multiport cards can also use interrupts other than
3 or 4, so they can be used along with standard COM1 and COM2 devices.

Ross Oliver
SCO Technical Support