Comments on: Apple PROM board, MEA/Apple TTY emulation update

By: Improved Apple Teletype Emulation « Mike's Hobby Blog

Improved Apple Teletype Emulation « Mike's Hobby Blog — Wed, 31 Dec 2014 17:12:47 +0000

[…] previous post showed how I attempted to connect the SCELBI TTY to an Apple IIe with an old serial card that […]

By: barrym95838

barrym95838 — Sat, 20 Dec 2014 04:55:45 +0000

Yeah, Woz wrote the scroll routine for compactness and flexibility, not speed. If you find that you can avoid dropping characters by narrowing or shortening your text window, you could wedge your own COUT with a custom quick-scroll routine using a BLOAD, two POKES and a CALL. I did something similar back in the day with a Hi-Res COUT for my ][+ that allowed bold-face, italic, and underlining, inspired by Bob Bishop’s AppleVision code. My Hi-Res scroll routine was naturally kind of slow, because I was moving almost 8K at a time, but for the text screen you could do something like:
SCROLL:
ldy #$27
SCR2:
lda $480,y
sta $400,y
lda $500,y
sta $480,y
lda $580,y
sta $500,y
…
lda $7d0,y
sta $750,y
lda #$a0
sta $7d0,y
dey
bpl SCR2
…
This method is hard-coded for a 40 by 24 screen, but is significantly faster than the monitor ROM routine because it doesn’t check for window boundaries or make any calls to VTAB.

Mike

By: Mike

Mike — Mon, 15 Dec 2014 18:14:37 +0000

Nice idea, reducing the window size, will reduce amount of data to scroll, speeding up the system.

By: D Finnigan

D Finnigan — Mon, 15 Dec 2014 02:08:57 +0000

Try making the Apple II text window shorter by two lines and see if you still lose data.