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+--- Thread: Someone's Fast & Easy Bitmap Graphics (/thread-1087.html)
Someone's Fast & Easy Bitmap Graphics - someone - 09-09-2026
When there's no rules and someone tinkers;
a slight mod of a 128K DRAM Coreboard and Alpha Plus Base board is configured to punch a neat hole in the memory map for easy PCG access.
e.g PCG being accessed at memory location 8000-BFFF or part thereof.
Bank #0 at 8000-87FF
Bank #1 at 8800-8FFF
Bank #2 at 9000-97FF
Bank #3 at 9800-9FFF
Bank #4 at A000-A7FF
Bank #5 at A800-AFFF
Bank #6 at B000-B7FF
Bank #7 at B800-BFFF
Doing this removes the onerous task of tracking & changing PCG banks continually.
A dedicated I/O port is used to augment the existing memory paging scheme to switch in the PCG.
In conjunction with someone's RA3 mod for 8X8 High PCG memory support and enabling Colour RAM, one can perform fast and easy bitmap graphics.
A useful configuration is:
0000-7FFF used for switched DRAM pages
8000-BFFF used for PCG
C000-EFFF used for DRAM (non-switched)
F000-F7FF used for CHAR or ATTR RAM
F800-FFFF used for COLRAM
RE: Someone's Fast & Easy Bitmap Graphics - MbeeTech - 10-09-2026
Excellent thinking Someone.
The 2 new Microbee models have something very similar already implemented, but it allows for PCG banks > 7 as there are 10 banks implemented, 4 planes deep.
Screen, Colour, Attr and font are also mapped in with Linear addressing mode.