MMM cartridge + MSX -> ColecoVision's games

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By gdx

Prophet (3090)

gdx's picture

01-09-2019, 08:38

All games I converted don't use the mapper of Megacartridge. I only tried to convert Pac-Man collection which uses this Mapper but without success.

Alexito, these versions seem to work:
https://mon-partage.fr/f/lelsNpmN/

Can you try please? I only initialize the Vram before start the game.

By ARTRAG

Enlighted (6283)

ARTRAG's picture

01-09-2019, 08:55

The sole way I see to support megacartridge mappers on msx is to patch the rom
The problem is that there isn't a simple way on msx to use a mapper in the top 16KB while IIRC the colecovision mapper works in 0x8000-0xFFFF with 8KB pages

By gdx

Prophet (3090)

gdx's picture

01-09-2019, 14:59

This version of Smurf seems better:
https://mon-partage.fr/f/OKKGNzMI/

I was able to reproduce the bug with the previous version but not with this one.

By ARTRAG

Enlighted (6283)

ARTRAG's picture

01-09-2019, 18:16

here are the specs of the colecovision megacartrige
https://drive.google.com/file/d/1qMKUQw-BMpte8yjBDRVRGxF342W...

I have to fix my previous post, rom pages appear at 0xC000-0xFFFF

By gdx

Prophet (3090)

gdx's picture

02-09-2019, 02:10

The graphic bug also occurs when I run the Colecovision Rom of Smurf on BlueMSX (Colecovision emulation). Shocked! So the bug was well caused by the RAM which is initialized with 00h instead of FFh. The bug had to happen with the Franky too.

All that remains is the missing sound of Burgetm to fix. Nobody has an idea about the cause?

By ARTRAG

Enlighted (6283)

ARTRAG's picture

02-09-2019, 08:18

Would it be possible to develop a rom mapper able to swap 8KB pages in 0x8000-0xBFFF and in 0xC000-0xFFFF ?
It could be very handy for running colecovision games on megacartridge
Maybe one could also implement the odd page select system in the megacartridge, that consists in strobing certain addresses to select a page

By gdx

Prophet (3090)

gdx's picture

02-09-2019, 10:35

If the RAM is initialized with FFh Smurf works but not Threshold. If the even bytes are set to zero and the odd ones to 0FFh, both games work and the others too apparently. So I updaded all COM files for MMM / Playsoniq. Next time I will update those for Franky.

COL4MMM.zip

ARTRAG wrote:

Would it be possible to develop a rom mapper able to swap 8KB pages in 0x8000-0xBFFF and in 0xC000-0xFFFF ?

According MegaCart pdf, the mapper is 16k. Segments can be selected only on the page 0xC000-0xFFFF. The page 0x8000-0xBFFF is fixed always on the last segment. However, it seems that many games use the module which also has RAM mapped.

By ARTRAG

Enlighted (6283)

ARTRAG's picture

02-09-2019, 14:04

mapped ram? AFAIK the sole ram expansion for colecovision is the SGM which provides up to 32 KB of ram in 0x0000-0x7FFFF (and the ay8910)

By ARTRAG

Enlighted (6283)

ARTRAG's picture

03-09-2019, 08:57

Sorry If I return on my proposal about supporting coleco megacartriges. The reason is that the majority of modern games for colecovision are using this mapper to overcame the 32KB limitation and there are plenty of good things developed in such a way.

The MMM has the SN76489AN and 1MB of paged ram with page size is 8KB that can be masked as rom.
Maybe it could be a good candidate for a semi automatic patch system.

Basically, each time the coleco code reads addresses FFC0h-FFFFh the patch should replace the opcode, typically
ld a,(FFXXh) ; 3 bytes

by something like

ld a,XXh-C0h
RST LABEL ; 3 bytes

where at LABEL you place
ld (80FFh),a
RET

Just brainstorming...

By gdx

Prophet (3090)

gdx's picture

03-09-2019, 11:14

I updaded all COM files for Franky / Playsoniq.

COL4MMM.zip

ARTRAG,
Actually only Super Pac-Mac Collection can be converted. The other games are games sold (often more expensive than MSX games) and it would be easier to ask for the source code to port them instead of converting, and among these games, there is a lot of conversion of MSX games to Coleco.

Both Coleco megacartrige and MMM use a 16k mapper but the bigger problem to convert Coleco games is interrupts.

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