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 Post subject: Re: MMC5 with CHR-RAM
PostPosted: Fri Jul 22, 2016 8:14 am 
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tepples wrote:
Write 8K, write to bank regs, write 8K more... Videomation manages it.

Fancy, never heard of that one! It's also not emulated correctly because Nintendulator mirrors CHR RAM after 8kB...
However, it's using mapper 13 which explicitly supports CHR RAM bank switching. Haven't seen anything alike on MMC5 yet (might just be an undocumented features, though).


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 Post subject: Re: MMC5 with CHR-RAM
PostPosted: Fri Jul 22, 2016 8:23 am 
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Mappers like these don't support CHR RAM bank switching as much as CHR bank switching in general. "Bank switching" just means driving upper address lines, and the mapper doesn't care whether the memory to which the address lines are connected is writable.


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 Post subject: Re: MMC5 with CHR-RAM
PostPosted: Fri Jul 22, 2016 4:29 pm 
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hellfire wrote:
tepples wrote:
Write 8K, write to bank regs, write 8K more... Videomation manages it.

Fancy, never heard of that one! It's also not emulated correctly because Nintendulator mirrors CHR RAM after 8kB...

Not sure what you're talking about - I just tested Videomation in Nintendulator and it worked just fine.

Nintendulator doesn't "mirror CHR RAM after 8KB" - most of its mappers simply don't map more than 8KB of RAM because that's all that most of them have. Notable exceptions include mapper 13 (Videomation, 16KB), 19 (Namcot 106, 32KB), 28 (Action 53, 32KB), 96 (Oeka Kids, 32KB), and 11/16/66/85 which use banked CHR RAM in the absence of CHR ROM and obey the NES 2.0 header to determine how much RAM is available.

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 Post subject: Re: MMC5 with CHR-RAM
PostPosted: Sat Jul 23, 2016 5:57 am 
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Quietust wrote:
Not sure what you're talking about - I just tested Videomation in Nintendulator and it worked just fine.

You're right, my fault - had it running in PAL mode so the timing was wrong and bankswitching happened at completely wrong positions.
Mirroring seems to happen only for header version 1 ("iNES_SetCHR_Auto1" in d_iNES.cpp). Thought I had seen it elsewhere but I was probably just confused again ;)


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