Turborom and Slow Videos

When the Advent TurboROM is installed on a Kaypro (with or without
ZCPR3) several new video features are enabled, as detailed in the
TurboROM manual, pp. 5-9 and 5-10.

The side-effects of one feature are not immediately obvious, so the
reasons for using the control sequences in Par. 5.6.1.4 are unclear, as
is the manner of implementing them.

The TurboROM default, which provides a 24-line scrolling window with a
locked 25th line (for clock or status display) has the unintended
side-effect of slowing down scrolling, whether through text, or large
directories.  It also trashes the bottom line display used by some game
programs (CLONE is a good example).

The file L25.SET is simply a hex string representing the video control
code <ESC> C 7.  Using PIP, the command PIP CON:=L25.SET will unlock the
25th line and speed up scrolling.  On my K10 it also cleans up the
scrolling nicely (much less cursor flashing & will-o'-the-wisp garbage
floating across the screen). Of course, this change is not very helpful
when you want a locked, real-time clock display line.

To switch back to the default locked 25th line, easiest is probably to
cold boot (removing the PIP command from any STARTUP alias--since I
don't use a clock, I included the unlock sequence in STARTUP for
convenience).  It's also possible to make an alternate L24.SET by using
DDT (or SPZ, or ...) to change location 0101h from 43h [C] to 42h [B].

There's probably a much easier way to handle this, and to access other
TurboROM features.  Perhaps some assembly-language maven will put
together a bells & whistles package.

CREDITS: Thanks to Derek McKay of Plu*Perfect Systems for patient
explanations of these arcane, and pointing to various possible
solutions.  TurboROM and its associated code is copyright by Advent
Products, Inc. and Plu*Perfect Systems.  The ziggurat of ZCPR3 is
copyright by Echelon, Inc.

  Fred Lieberman (N7AX)
  voice tel.  (408) 338-2914

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