From: richvh@citlink.net   
      
   Jan Vanden Bossche wrote:   
   > Neil,   
   >   
   > I do remember working seriql with my models III and 4P - most with the   
   > latter - and I never had a problem with scrolling  19200bd.   
   >   
   > Actually, the serial interface of the models III an early model 4s was   
   > identical. It was with the models 4 (GA), 4P (non-GA and GA) and 4D that the   
   > serial card was build-in. But again, no problem scrolling @19200.   
   >   
   > I even have a terminal program, producing ANSI and PC-graphics on a 30-lines   
   > display, and that scrolled fine at 9600. I can't remenmber I tried it at   
   > 19200. I think you underestimate the power of the early TRS-80's.   
      
   That would be ANSITerm4 - and I had to use several tricks to minimize   
   dropped characters.  The problem with dropped characters at high speeds   
   isn't related to the scrolling (at least, not solely, or just having an   
   input buffer would cure it); the serial input interrupt is lower   
   priority than the clock interrupt, and LDOS 5 and TRSDOS/LSDOS 6 do a   
   lot of stuff (mostly keyboard scan) during the clock interrupt.  I   
   inserted my own interrupt check at the start of the interrupt string,   
   and used a HUGE input buffer, but even so, if you have continuous input   
   for long enough (viewing a long text file, for instance), you would   
   eventually overflow the buffer (scrolling the graphics screen is   
   s-l-o-w.  It can't keep up at higher baud rates.)   
   >   
   > Like I said, most of my experience comes from models III and models 4. I do   
   > have a serial interface on my I, but I hardly ever used it. A friend of mine   
   > said that - because it wasn't interrupt-driven - that he could use it as a   
   > barcode-port. ANd it worked!   
   >   
   >   
   > Greetings from the TyRannoSaurus   
   > Jan-80   
   >   
   >   
   > "N Morrison"  wrote in message   
   > news:1186874812.118916.254020@z24g2000prh.googlegroups.com...   
   >> On Aug 11, 4:03 pm, "winston19842...@yahoo.com"   
   >>  wrote:   
   >>   
   >>> Again, connection speed != throughput.   
   >>> I just wonder how you'd write software that would go to top of screen   
   >>> and start overwriting without scrolling, unless it received a "soft   
   >>> command" that would HOME it without clearing the screen? Which may   
   >>> happen if you get a data overrun, aren't checking and return a   
   >>> character such as a HOME from the remote. Or sending a binary file   
   >>> with said character.   
   >> The screen is memory mapped to &H3C00 - &H3CFF so you can handle it as   
   >> you wish.   
   >>   
   >   
   >   
      
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