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VT09 RAM
http://forums.nesdev.com/viewtopic.php?f=3&t=16725
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Author:  NewRisingSun [ Wed Nov 22, 2017 5:13 am ]
Post subject:  VT09 RAM

The VT09 variant of the OneBus-type Famiclones has 4 KiB instead of 2 KiB of main CPU RAM at offset $0000 in CPU memory. FCEUX apparently uses mapper 256 for OneBus, and I intend to follow that precedent. In the NES 2.0 format, should this additional RAM be denoted as a submapper or as 2 KiB PRG-RAM, even though this additional RAM is part of the main unit (or rather part of the main chip) and not the game? Some OneBus images of course have the normal 8 KiB of WRAM at $6000, so if one went for the PRG-RAM field, the PRG-RAM size would then implicitly determine its offset as well, which seems kind of hacky to me. Given that several OneBus images are multicarts consisting of NES-era games that may depend on RAM being mirrored four times in the $0000-$1FFF range, just always emulating the additional 2 KiB does not seem safe.

Opinions?

Author:  lidnariq [ Wed Nov 22, 2017 5:22 am ]
Post subject:  Re: VT09 RAM

Most of the fields in the NES2.0 header are describing properties of the cartridge, not the console. And if you use the RAM size field here to describe the console, there's no space to describe the cartridge.

Author:  Dwedit [ Wed Nov 22, 2017 3:22 pm ]
Post subject:  Re: VT09 RAM

The VS system and PAL region flags describe the console, and not the game.

Author:  zzo38 [ Sat Nov 25, 2017 7:53 pm ]
Post subject:  Re: VT09 RAM

Dwedit wrote:
The VS system and PAL region flags describe the console, and not the game.
Yes. If there are unused bits in those section, then maybe use some of those if necessary?

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