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From: ajq@mace.cc.purdue.edu (John O'Malley)
Newsgroups: comp.sys.mac
Subject: Re: Mac II to mainframe via ISN at 19.2K isn't working!
Summary: Was it the Mac's software?  Nope, the RS422 port was the culprit
Message-ID: <453@mace.cc.purdue.edu>
Date: 17 Aug 88 16:11:04 GMT
Reply-To: ajq@mace.cc.purdue.edu (John O'Malley)
Organization: Personal Computing Learning Resource Center, Purdue University
Lines: 26

In a recent article I write:
>We've got a Mac SE and a Mac II hooked up to our Unix- and CMS-based mainframes
>via an AT&T Integrated Services Network (ISN) line.  The setup runs perfectly 
>at 9600 baud using MacKermit 0.9(40) (favorite software) as well as 
>MacTerminal 2.2 and Red Ryder 9.4.
>
>When we attempted to bounce the ISN box up to 19200 baud, we found that none
>of the software worked.  

Turns out it was a hardware problem.  We had a short-haul modem connecting
our Mac to the ISN line.  This method of connecting doesn't work at high
speeds ... the Mac's RS422 port couldn't drive the short-haul modem.  
Apparently the RS422 port is capable of driving the ISN line at 19.2K without
any additional hardware ... that's how I'm logged in now.  All this is what
I've been told by our hardware people.

>One of my coworkers (an IBM-type person) had a good laugh when we tested
>our Mac's ISN line with a lowly IBM Convertible running Kermit-MS at 19.2K, 
>and it worked perfectly ... seeming to prove the problem is on the Mac's end.

I'm happy to hear that it sorta wasn't the software's problem.  So much for
cheap IBM's.  :-)  Thanks for your responses.


John O'Malley         \ Personal Computing       \ Purdue University \ (317)
mace.cc.purdue.edu!ajq \ Learning Resource Center \ Computing Center  \ 494-9944