Path: utzoo!utgpu!watserv1!maytag!xenitec!zswamp!root
From: root@zswamp.uucp (Geoffrey Welsh)
Newsgroups: comp.dcom.modems
Subject: 4.77MHz PC sufficient for 19200 bps modem?
Message-ID: <243.2861EA82@zswamp.uucp>
Date: Fri, 21 Jun 91 03:08:25 EDT
Organization: Izot's Swamp BBS (FidoNet), Kitchener, Ontario

In a letter to All, Jonathan Hardwick (jch+@cs.cmu.edu ) wrote:

 >A housemate has an original Big Blue IBM PC, running at the 
 >blazing
 >speed of 4.77MHz.  We want to use this as a dumb terminal to 
 >access
 >our university workstations.  The university offers 2400 bps 
 >service
 >with MNP level 5, and a 9600 bps or 19200 bps MCN service 
 >using DOV
 >modems.  We'd really like the extra speed if possible.  Is 
 >the PC
 >going to be able to keep up with 19200 bps?  How about 9600 
 >bps?

Question: Will a 4.77 MHz 8088 do 19,200 (9600) bps?

Answer: 9600 probably, 19200 probably not.  However, install an NS16550AFN 
chip in place of the 8250 or 16450 chip on your serial port (and use software 
which supports it), and the problem's solved.

Comment: The only DOV (data over voice) modems I know of are devices which can 
transmit data, modulated at high frequencies, over existing direct wires.  
These are useful where a telephone system (e.g. PBX) is already installed and 
you want to put terminals on people's desks without rewiring the world.  They 
don't work over dialup lines.

 >Oh, and if the PC *can't* keep up, what sort of motherboard 
 >upgrade would we need?  10 MHz 8086?  80286?

   There are a *lot* of variables involved.  The best (and cheapest) solution 
is the 16550.
 

--  
Geoffrey Welsh - Operator, Izot's Swamp BBS (FidoNet 1:221/171)
root@zswamp.uucp or ..uunet!watmath!xenitec!zswamp!root
602-66 Mooregate Crescent, Kitchener, ON, N2M 5E6 Canada (519)741-9553
"He who claims to know everything can't possibly know much" -me