mapped roms and page 0

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Por ARTRAG

Enlighted (6280)

imagem de ARTRAG

27-02-2019, 17:04

Question: what should I expect if I plug a rom with e.g. konami mapper in e.g. slot 1, and I swap out the bios putting in page 0 the slot 1 content?
Does the rom mirror its content in page 0 ? If yes, what are the mapper banks that I should expect to see?

Maybe I'm going to reinvent the wheel here, but in the past I've used the ram coping a rom page in it and I've not found a clear answer on the net.

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Por NYYRIKKI

Enlighted (5399)

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27-02-2019, 17:11

ARTRAG: I really suggest you to take a look this great tool called Super-X
See how hard this kind of thing is to solve:

BLOAD"SUPER-X.LDR",R
_@ ' start the program
D0#1
( = Use HEX-editor to address 0 slot 1)

Por ARTRAG

Enlighted (6280)

imagem de ARTRAG

27-02-2019, 17:33

super-x is ultra super cryptic to me Tongue (and I should use it on a real hw to test the case, which I cant at moment...)

Por NYYRIKKI

Enlighted (5399)

imagem de NYYRIKKI

27-02-2019, 17:39

ARTRAG wrote:

super-x is ultra super cryptic to me Tongue (and I should use it on a real hw to test the case, which I cant at moment...)

Don't let my videos to fool you, if you read the manual once I'm sure you'll be friends forever. Smile You don't even need to learn all at one go.

... but yes indeed... I'm also not right now on front of my MSX, so I can't really test this... IIRC page 0 is not used (I would guess the cartridges use /CS12 signal to attach mapper), but I might very well be wrong as well... I really don't have any strong memories about this subject.

Por ARTRAG

Enlighted (6280)

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27-02-2019, 18:20

Anyway, mine was just a sort of teorichal speculation.
Even if page 0 was mirrored, it would have been of reduced use, because the same mapper registers (which one?) would have affected two banks in two pages...
So if you gain direct access to isr even on machines with 32KB of ram, you loose a mapper bank out of 4.

Por Victor

Champion (470)

imagem de Victor

27-02-2019, 18:54

Those mappers (Konami, Konami SCC, ASCII8, ASCII16) are only visible in (4000h-BFFFh)

Por Jipe

Paragon (1366)

imagem de Jipe

27-02-2019, 19:45

with shem you can see bank of mapper if you have a slot expander for cutting SLOTSL
just Konami mapper have the page 0 - 3fff mirrored on 4000 - 7fff

Por ARTRAG

Enlighted (6280)

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27-02-2019, 20:50

Have you verified the mirroring for Konami mappers on real hw?

Por Victor

Champion (470)

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27-02-2019, 21:55

ARTRAG wrote:

Have you verified the mirroring for Konami mappers on real hw?

I've tested now in real HW with a real Gradius cartridge and Jipe is right!!! Really surprising!!

So, the pages you're seeing in 4000h-8000h are mirrored in 0-4000h, BUT you can't select page in 02000h adress...

Por ARTRAG

Enlighted (6280)

imagem de ARTRAG

27-02-2019, 22:33

Nice finding. This is very interesting, as openmsx doesn't show that behavior but just a FFh area.
It should be fixed in emulators.
Now there is a way to override the bios also on machines with 32KB of ram...

Por ARTRAG

Enlighted (6280)

imagem de ARTRAG

27-02-2019, 23:11

Anyway I would have expected to see the other two banks, those at 8000h-BFFFh...
Are you sure that you are looking at those at 4000h-7FFFh?

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