Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!sdd.hp.com!spool2.mu.edu!sol.ctr.columbia.edu!emory!rsiatl!jgd
From: jgd@Dixie.Com (John G. DeArmond)
Newsgroups: comp.unix.sysv386
Subject: Re: internal Telebit, SCO Unix 3.2, 80 bytes/sec???
Message-ID: <5626@rsiatl.Dixie.Com>
Date: 4 Jan 91 18:50:17 GMT
References: <24558@dime.cs.umass.edu> <130@limbic.ssdl.com>
Organization: Rapid Deployment Systems (making go-fast things and things that-go fast)
Lines: 35

gil@limbic.ssdl.com (Gil Kloepfer Jr.) writes:

>In article <24558@dime.cs.umass.edu> williams@cs.umass.edu writes:
>>I am calling SCO's sosco system for testing and the Systems entry is
>>set to use the dialTBIT dialer with the speed set at 19200.  uutry
>>reports CONNECT FAST, but the xferstats shows that I'm only getting
>>76 bytes per second on large transfers!

>The internal Telebits only have the 16450 UARTs in them, so you would
>need to unsolder the 16450 and replace it with a 16550 in order to
>really get good performance, even with FAS.  I had a friend who did
>this, and now the thing flies.

This is absolutely correct.  Telebit was brain damaged not to use 
the 16550.  Another modification that I consider mandatory for internal
modems of any sort is to add a switch to either the send or receive
data line from the uart to the modem so that one can interrupt the data
flow.  If you don't and the modem gets to chatting with a getty, you'll
find that (at least with ISC unix) the conversation takes up all the 
processor time and you'll be unable to even process keystrokes.  Big
Red Switch time.  I've observed this even with 2400 baud modems.

Plus, as KE4ZV (hi gary) can verify, an internal modem will conduct
a lot of lightening into your machine and turn it back into silicon
raw materials minus all the blue smoke.  Of the 2 people I know of who
have been heavily zorched by lightening in the last year, both had it
come in over the phone line and both lost very expensive computers.

John

-- 
John De Armond, WD4OQC        | "Purveyors of speed to the Trade"  (tm)
Rapid Deployment System, Inc. |  Home of the Nidgets (tm)
Marietta, Ga                  | "To be engaged in opposing wrong offers but 
{emory,uunet}!rsiatl!jgd      |  a slender guarantee of being right."