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2007-05-28 13:58

jonathon
Account closed

Registered: May 2007
Posts: 4

Difference between hires and multicolor bitmap modes?

Hi all,

long after selling my C64 and Amiga, I'm back to write my first ever intros.
:-)

I'm not getting through my head the diff between regular hires bitmaps and multicolor. I know multicolor trades resolution for extra color, and also uses color ram, but I can't quite connect the dots, pun intended.

I've been able to load a koala bitmap and display it, but only multicolor, not hires. And I still don't understand how the color data is all connected.

Would someone kindly break down the two modes, the register settings, and what/where the data are stored?

THX!

2007-05-28 15:27

Mace

Registered: May 2002
Posts: 1799

I'm not sure this is the right place to fully explain how the colour system works...

To begin with, you can't display a Koala picture in hires.

The colours of hires are only in the screen memory, the colours of multicolour are both in the screen memory AND the colour memory.

The location of the bitmap and the screen memory depend on the settings of $d018 and $dd00.
Bitmap starts at either in bank 0 ($0000 or $2000), bank 1 ($4000 or $6000), bank 2 ($8000 or $a000) or bank 3 ($c000 or $e000).

Screen memory is always in the same bank as the bitmap but can be at bankstart+$0000, +$0400, +$0800, +$0c00, +$1000, +$1400, +$1800, +$1c00, +$2000, +$2400, +$2800, +$2c00, +$3000, +$3400, +$3800 or +$3c00.

Colour memory is ALWAYS at $d800.

2007-05-28 15:44

jonathon
Account closed

Registered: May 2007
Posts: 4

Thanks for the reply. I'll need to find that color mode info somewhere.

Does anyone use hires anymore, or is it almost always multicolor bitmaps?

2007-05-28 15:52

Cruzer

Registered: Dec 2001
Posts: 1048

Multicolor can be switched on/off for both char mode, bitmap and sprites.

For char/bitmap, bit 4 of $d016 controls multicolor, i.e. xxx0xxxx = off, xxx1xxxx = on.

When turned off ("single color mode") there's only two colors (foreground and background) which can be set individually for each 8x8 char in bitmap mode. To get more colors, the bitmap can be turned into FLI so the char screen can be switched each rasterline, which reduces the area with the same color to 8x1 pixels. This can furthermore be combined with a layer of sprites, which makes it possible to create some hires gfx that almost looks like it has the same color flexibility as multicolor.

2007-05-28 16:32

Frantic

Registered: Mar 2003
Posts: 1648

Although perhaps too summarized to make real sense to a beginner, the following page will tell you something:

http://unusedino.de/ec64/technical/aay/c64/vicintpr.htm

Also check the collection of links on the codebase wiki:

http://wikholm.dyndns.org/~cswiki/doku.php?id=links:start

Something there might help you out.

2007-05-28 16:49

Oswald

Registered: Apr 2002
Posts: 5094

the screen is divided into character places. on given character locations the bits will read their color from:

hires mode:

bit 1: screen mem low (at given character place)
bit 0: screen mem high (at given character place)

multicolor mode

bit 00: $d021, background color
bit 01: screen mem low (at given character place)
bit 10: screen mem high (at given character place)
bit 11: d800 (at given character place)

high and low means the upper and lower 4 bits of the byte.

2007-05-31 14:36

jonathon
Account closed

Registered: May 2007
Posts: 4

Excellent, thanks!

2007-06-01 04:52

Fungus

Registered: Sep 2002
Posts: 686

also go to project64 and dl Mapping The C64, Programmers Reference Guide, etc. Invaluable references to anyone coding.

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