[Coco] tetris question
robert.gault at worldnet.att.net
Sun Jan 17 18:46:01 EST 2010
Jeremy Michea wrote:
> I'm trying to play my tetris rom pack on my 512k coco 3 and on 2 different composite tv's its coming out black and white. Can't find a way to change it. Anyone know why and how to fix this?
> Coco mailing list
> Coco at maltedmedia.com
I don't have the pak so can't try it on a real Coco3.
I mounted an image in MESS and looked at the initial code for the pak.
It starts with a test that seems problematic to me.
a@ sta $ffbf
bne $c01a branches to PMODE code Coco1 or 2, artifact colors
goes to HSCREEN code Coco3, real colors
When I run this test on my Coco3
30 POKE M,I:PRINT PEEK(M);
I find that bit6 at $FFBF is locked high so the value at $FFBF will
never equal that in regA. In fact this true for all the palette
registers. Makes me wonder if the pak can correctly tell what type of
Coco is in use.
Anyway, assuming the pak recognizes a Coco3 is present, it then starts a
320x192x4 HSCREEN. Unless the game has a specific instruction for
holding down a key when starting this pak, the colors used will be grays
on a composite monitor; black, white, red, and blue on an RGB monitor.
There might be some artifact colors with an NTSC composite monitor which
I can't tell, not having the pak.
More information about the Coco