Date   : Wed, 18 Sep 1991 19:39:29 PDT
From   : pallio.UUCP!dg@mis.ucsf.EDU (David Goodenough)
Subject: Re: Qterm/vt100

fzsitvay@techbook.COM sez:
> In article <9460729@ub.cc.umich.edu> Steve.Graham@UB.CC.UMICH.EDU writes:
>> I am using the cpm QTERM comm program with its vt100 emulator to talk to
>> our mainframe (UB-MTS) full-screen message system.
>> I am running QTERM on a Kaypro-II, a slow machine.
>> The problem I am having is that even at 1200 baud  sometimes the vt100
>> codes coming in from MTS go by too fast for the Kaypro to keep up, and the
>> screen gets scrambled.  I checked this out at 300 baud, and at that speed
>> it works first time, every time, but that is impractical.
>
>   most cp/m com programs use an "overlay" to allow the same executable code
> to work on different serial port hardware.  your best bet would be to
> rewrite the overlay so it does interrupt driven input/output.  the hardware
> is definately able to support it.

Agreed. I'm in the process of trying to write an interrupt driver for the
Kaypro, the only problem (as far as I can tell) is that I need to do some
other "interrupt related" things myself, because I'm messing with the
interrupts, and may wind up screwing something up.

However it ought to be possible.
 
>  but the reason why i said this might not work is because interrupt driven
> input will allow the terminal/computer to store characters it otherwise
> would miss in a circular buffer in RAM.  If the serial port baud rate is
> too fast for the processor to handle, then interrupt driven input won't do
> a scrap of good.

Also agreed - you're presimably talking about the case when the text data
is arriving too fast. However most all CP/M systems can dump printable
characters to the screen in almost no time at all. It's things like scrolling
the screen and some of the other strange functions that start taking time.
provided there's a reasonable amount of text output as text, it ought to
work OK. Consider the C128 - that's slower than the Mississippi in the
summertime getting text to the screen, but it can still keep up at 2400
with an interrupt driven serial driver.
 
>   someone may have already gone ahead and written an interrupt driven 
> overlay for QTERM for the kaypro II, so if you can find someone who has one
> you may have the easy way out there.

I'd love it if they had - cuz it'd save me a pile of work. However, I'll
get this beaten senseless yet. Either that or die trying. :-/
 
>  but if you can't find one, i'll help you with it.  I have a kaypro II 83,
> .....

Humm. You wanna be a beta tester for the driver when I get it done?
-- 
       dg@pallio.UUCP - David Goodenough               +---+
                                               IHS     | +-+-+
       .....!wet!pallio!dg                             +-+-+ |
AKA:   dg%pallio.UUCP@cs.sfsu.edu                        +---+


End of INFO-CPM Digest V91 Issue #164
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