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From: papa@pollux.usc.edu (Marco Papa)
Newsgroups: comp.sys.amiga
Subject: Re: Amiga serial questions
Message-ID: <5568@oberon.USC.EDU>
Date: Sat, 5-Dec-87 16:20:51 EST
Article-I.D.: oberon.5568
Posted: Sat Dec  5 16:20:51 1987
Date-Received: Sun, 13-Dec-87 09:29:31 EST
References: <8712050831.AA11465@cory.Berkeley.EDU>
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Reply-To: papa@pollux.usc.edu (Marco Papa)
Organization: Felsina Software, Los Angeles, CA
Lines: 48

>>  ...
>> will explain "sustained".  8 hours of continuous 19.2K transmission with no
>> ^S/^Q or any other software handshaking, no hardware handshaking, data is
>> always being sent (no pauses at all).  Dropping even a single character is
>> devastating.  Some constraints on multitasking and windowing are acceptable.
>> Scrolling is mandatory, Tek emulation (at speed) very desirable.  PD/shareware
>> with source is preferred as this could become part of something MUCH bigger
>> but I am willing to talk to commercial vendors.

Matt responds:
>	Don't be silly.  Even Tek terminals have flow-control, and assuming
>all 55 Meg will get through without an error is ridiculous.  The Amiga can
>read data at that speed, but not scroll at that speed.  Sure you could
>dynamically buffer the data, but *any* computer would get behind... not
>for simple things like line drawing, but what about area fills and other
>advance functions?

Having written a commercial Tek emulator for the Amiga, I'd like to comment
on this.  The A-Talk Plus Tek 4010/4014 emulator, in GRAPHICS drawing mode, 
can keep up with 9600 bauds with NO loss of characters or overrruns in both 
640x400, 640x200, and either 1 or 2 bitplanes [Note the 640x200 non-interlaced
mode will be available in the next OXXI version].  I have tested this by
sending a 1Meg plot file (made up of lots of plots, with clearscreen commands
between them) between an IBM AT and the Amiga at the max IBM speed, which is
9600 bauds.  I haven't tried between two directly connected Amigas, but that
test is on my queue. Note that I did NOT use any handshake protocol, either
Xon/Xoff or CTS. All graphics is done using the blitter, so I suppose it is
possible that it will indeed keep up with 19,200.  These kinds of
speeds are usually not possible with real "tek" terminals, and DEC or clone
emulators, which are usually controlled by 8086s and have no blitter chip in
them.  Most manuals will tell you that one has to use X-on/X-off at speeds 
higher than 1200 bauds!

Note that Tek 4010/4014s (and emulators) DON'T scroll, so that is not a 
problem).  

A VT100 or similar emulator is another story.  We have tested ours, and 
found that with input data that includes an "average" amount of scrolling,
the emulator will keep up with 7000-8000 bauds.  Again this is still better
than most "hardware" emulators that will need Xon-Xoff to keep up with high
speeds.  For the purpose of speed we included a 1-bitplane screen mode, so
that less data has to be moved when scrolling.

I'll try similar tests on our [unreleased] Tek 4105 (8-color) emulator an see 
what I get. This does color pattern and area fill, though these are also done 
through the blitter.

-- Marco