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From: cccook@deneb.ucdavis.edu.UUCP
Newsgroups: comp.unix.xenix
Subject: Re: Multi-port serial card
Message-ID: <294@ucdavis.ucdavis.edu>
Date: Thu, 24-Sep-87 18:24:28 EDT
Article-I.D.: ucdavis.294
Posted: Thu Sep 24 18:24:28 1987
Date-Received: Sat, 26-Sep-87 14:14:53 EDT
References: <204@ivory.SanDiego.NCR.COM>
Sender: uucp@ucdavis.ucdavis.edu
Reply-To: cccook@deneb.ucdavis.edu.UUCP (Doug Cook)
Distribution: world
Organization: University of California, Davis
Lines: 33
Summary: There's a lot you can do...

In article <204@ivory.SanDiego.NCR.COM> mike@ivory.UUCP (Michael Lodman) writes:
>I would like to have multiple serial ports on my Xenix PC. What are people 
>using in the way of add in boards for such things?

There are quite a lot of serial multiplexors available for the multiuser PCs.
I am currently using a Computone ATvantage X-4P four-port multiplexor in my
PC. I am very pleased with the product, and it wasn't expensive. It has an 
on board 8088-2 and two Z-80's to offload the I/O processing from my CPU, so
even with all the ports in use, I don't see a lot of degradation in speed.

Computone also makes 8-channel boards and tells me they are about to release
a 16-channel mux with its own 80286. Another company, Digiboard, makes excellent
multiplexors as well.

Multiplexors offer several advantages over multiple serial ports. First, they
take up only one interrupt & one slot, whereas your standard serial port takes
up one interrupt per port. Plus the intelligent multiplexors will handle a lot
of I/O processing on the board, rather than sending it through to the CPU. The
price of a multiplexor (per port) is only slightly higher than buying several
serial cards, and in some cases it might be lower. You should check into it.


			-Doug

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