Path: utzoo!utgpu!cs.utexas.edu!wuarchive!zaphod.mps.ohio-state.edu!samsung!xanth!ames!vsi1!daver!indetech!jack!mvp
From: mvp@jack.sns.com
Newsgroups: alt.hackers
Subject: Re: test
Message-ID: <1991Mar2.032644.2884@jack.sns.com>
Date: 2 Mar 91 03:26:44 GMT
References: <978@creatures.cs.vt.edu>
Sender: mvp@jack.sns.com (Mike Van Pelt)
Organization: Systems'n'Software
Lines: 41
Approved: by.me

In article <978@creatures.cs.vt.edu> brand@csgrad.cs.vt.edu (Jeff Brandenburg) writes:
>ObHack:  retapping the divide chain on a TRS-80 so the heartbeat interrupt
>came 4 times as frequently as normal, fast enough to keep up with chars from
>a 1200 bps modem rather than only 300 baud.  Oh, and the interrupt-driven
>serial driver, of course.  The BAD old days, but sometimes I miss being able
>to just open up the machine and *fix* it if I didn't like the design.  Try
>that with an 8-layer board and surface-mount technology...


Those were the days... All the stuff I did to my TRS-80:

Doubled the clock speed

Added an extra 2102 for lower case

Built a board to replace the character generator with a
custom-programmed 2716 for *decent* lower case.  Just for
the fun of it, I sacrificed the "graphics", and put the
Greek, Russian, and Hebrew alphabets in the upper half
of the ROM.  Eventually I changed that back; too many games
wouldn't work.

Added a board from Exatron to put 64K in the keyboard.
(I never did get an expansion interface.)

Hacked the video circuitry to test vertical retrace from an
IO port, so I could write a program to test for retrace, and
avoid snow on the screen.

While I was at it, used an output line to switch 32 column
mode from even locations to odd locations, giving the effect
of two pages of video memory in 32 column mode.

Add the Dennis (?) mod from 80 Microcomputing to de-snow
the screen for everything by adding wait states.

-- 
  Caution: Thermostellar device.          Mike Van Pelt
       Handle with care.                  Headland Technology
 Do not expose to first-semester          (was: Video Seven)
     Philosophy students.                 ...ames!vsi1!v7fs1!mvp