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Path: utzoo!watmath!clyde!rutgers!uwvax!puff!schumann
From: schumann@puff.UUCP
Newsgroups: comp.sys.apple
Subject: Re: comm software advice sought
Message-ID: <498@puff.WISC.EDU>
Date: Sun, 15-Feb-87 20:22:01 EST
Article-I.D.: puff.498
Posted: Sun Feb 15 20:22:01 1987
Date-Received: Mon, 16-Feb-87 03:57:55 EST
References: <8702111802.AA00876@nprdc.arpa>
Organization: U of Wisconsin CS Dept
Lines: 25
Summary: 9600?? You gotta be kidding

In article <8702111802.AA00876@nprdc.arpa>, trejo@NPRDC.ARPA writes:
> I have an Apple IIc that I'd like to use as a terminal that talks to
> a VAX or a Masscomp over a local high speed modem (9600 baud).... 
> ... Something like VT52 or VT100 emulation would be fine.

The Apple //c will have a VERY difficult time recieving data at 9600 baud.
One character at 9600 takes 1/960th sec (1.042 ms) +/- 2%.
Using iterrupt mode, the //c can take up to 300 microseconds to respond,
add about 40 for ProDOS (assuming priority one), 100 to queue the character,
and add up to 140 for the //c to return to the interrupted program.

That comes to 580 microseconds or almost 56% time spent on queueing
characters, never mind printing them.  I have found the //c can go up to
3600 with no difficulty, and 7200 in a pinch.

You could write your own interrupt handlers, and replace the interrupt
vectors in bank-switched ram at $FFFE, which automatically get changed
to point to the ROM handler when just about anything happens (an
exaggeration).

Anyway, I know of at least three 9600 baud modems.

Racal-Vadic 9600VP	9600,7200,4800		$1495	V.29
EVI UPTA 96		9600,7200,4800		$895	V.29
Telebit Trailblazer	9600          		$2300   Special