COCO3: HOW TO MAKE THE BORDER BLACK IN 256X192 4 COLOR PROGRAMS!!!

swallis7 · May 9, 2020

HOW TO MAKE THE BORDER BLACK IN 256x192 4 COLOR PROGRAMS!!!
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I figured out how to make the border black instead of white in 256x192 4 color
games/programs!!! (Running Color Computer 1/2 games on a CoCo 3.)

This works in RGB and CMP modes. I have the palette set to RGB colors,
so this effectively does an "RGB Patch" too!

It has the added benefit of being able to change the
Black/Blue/Red/White colors to whatever palette colors you want (some
game just don't look good in Black/Blue/Red/White).
I haven't figured out how many colors there are to choose from yet.

And you can change the border color to whatever palette color you want!

So far I've tried this with Donkey King, Downland CC3 and a couple of
other games, but it should work on any 256x192x4 program you want.

I did this using MAME 0.187 and it works in VCC.
I do not have a real CoCo 3 to try this out on.
I also did this years ago on a real CoCo 3, it seems like there were
less commands required then, so maybe this can be simplified??

MY TEST DISC:
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It is the "Disk EdtAsm+ 1.0" disk (for testing) with these files added:

VM.BAS Sets the video mode (see the code below).
VM.ASM Sets the video mode (see the code below).
VM.BIN Sets the video mode (only good for Donkey King unless recompiled).
DONKEY.BIN Donkey King.
DONKEY2.BIN Donkey King with the video mode commands at $340D-$341A removed (for testing).
GETSMART.BAS A Barbara Feldman picture (for testing whether the screen is displaying the way you want).

TO TRY THIS OUT:
----------------

For Donkey King: Just insert my test disc and RUN"VM.BAS".
(Or use your Donkey King disc and run the BASIC code below.)

Since this is not a perfect fix for Donkey King (it goes from graphics
mode to text mode & back to graphics mode when its first started);
press Enter, wait 7 seconds, press 1, press Y to make the game start.

For Downland CC3: LOAD"VM.BAS", edit line 110 and change the Vertical
Offset as stated, insert the Downland CC3 disc, then type RUN.

NOTE1: "VM.BAS" is all that is needed for some games (Donkey King is a
VERY friendly game to test with).
"VM.ASM" is something I made to experiment with, since some ML games
write over any BASIC program in memory when loaded.

NOTE2: It's funny to note that when you set the video mode with this
($FF99), then Donkey King sets it the CoCo 2 way ($FF22) it seems to
basically get ignored... but not completely... hmmm.

Enjoy!

"VM.BAS"
--------

10 ' THIS SETS THE COCO3 VIDEO MODE TO 256X192 4 COLORS.
20 ' TO TRY IT ON ANOTHER GAME:
30 ' CHANGE THE VIDEO MODE?, VERTICAL OFFSET AND COLORS AS NEEDED/DESIRED.
40 '
50 LOADM"DONKEY"
60 '
70 POKE&HFF90,126 'COCO COMPAT MODE
80 POKE&HFF91,0 'MMU-NOT NEEDED I GUESS
90 POKE&HFF98,128 'BIT PLANE GRAPHICS-NOT ALPHA TEXT
100 POKE&HFF99,9 'VIDEO MODE-256X192 4 COLORS
110 POKE&HFF9D,224:POKE&HFF9E,64 'VERTICAL OFFSET-DOWNLAND CC3=224,128
120 POKE&HFFB0,0:POKE&HFFB1,11:POKE&HFFB2,7:POKE&HFFB3,48 'CMP PALETTES-BLACK,BLUE,RED,WHITE
130 POKE&HFFB0,0:POKE&HFFB1,9:POKE&HFFB2,36:POKE&HFFB3,63 'RGB PALETTES-BLACK,BLUE,RED,WHITE
140 POKE&HFF9A,0 'BORDER COLOR!
150 '
160 EXEC

"VM.ASM"
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THIS SETS THE COCO3 VIDEO MODE TO 256X192 4 COLORS.
Not the prettiest code, I tried in on Donkey King.
To try it on another game:
Change the "ORG $3000" to the address you want this to load at,
change the "JMP $3203" to the Start Address of the game you are using,
change the Video Mode, Vertical Offset and Colors and needed/desired.

00010    ORG $3000
00020 BEGIN   JMP START
00030    FDB DONE-BEGIN
00040 * COCO COMPAT MODE
00050 START   LDA   #$7E
00060    STA   $FF90
00070 * MMU-DON'T NEED THIS
00080    LDA   #$00
00090    STA   $FF91
00100 * BIT PLANE GRP-NOT ALPHA TEXT
00110    LDA   #$80
00120    STA   $FF98
00130 * VIDEO MODE-256X192 4 COLORS
00140    LDA   #$09
00150    STA   $FF99
00160 * VERTICAL OFFSET 1
00170    LDA   #$E0
00180    STA   $FF9D
00190 * VERTICAL OFFSET 2
00200    LDA   #$40
00210    STA   $FF9E
00220 * RGB PALETTE - BLACK
00230    LDA   #$00
00240    STA   $FFB0
00250 * RGB PALETTE - BLUE
00260    LDA   #$09
00270    STA   $FFB1
00280 * RGB PALETTE - RED
00290    LDA   #$24
00300    STA   $FFB2
00310 * RGB PALETTE - WHITE
00320    LDA   #$3F
00330    STA   $FFB3
00340 * BORDER COLOR!
00350    LDA   #$00
00360    STA   $FF9A
00370 * EXEC DONKEY KING...
00380    JMP   $3203
00390 DONE   EQU   *
00400    END   START