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How to detect MMC1 Revisions?
http://forums.nesdev.com/viewtopic.php?f=3&t=9657
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Author:  Zelex [ Mon Dec 31, 2012 3:02 pm ]
Post subject:  How to detect MMC1 Revisions?

The simplest approach I suppose would be change based on CRC and then just have a database. Whats the standard method here?

Author:  tepples [ Mon Dec 31, 2012 3:21 pm ]
Post subject:  Re: How to detect MMC1 Revisions?

MMC1A is mapper 155. MMC1B and MMC1C are mapper 1.

Author:  3gengames [ Mon Dec 31, 2012 4:40 pm ]
Post subject:  Re: How to detect MMC1 Revisions?

What about plain MMC1? But I have a test ROM that detects the banks work, then provides start up info and WRAM info. It's on the forums here a few times, should be easy to find.

Author:  tepples [ Mon Dec 31, 2012 4:59 pm ]
Post subject:  Re: How to detect MMC1 Revisions?

Correct me if I'm wrong, but I think MMC1 and MMC1A behave the same: no PRG RAM disable bit. MMC1B has a PRG RAM disable bit but boots in an unpredictable state; MMC1C always boots in disabled state. Only two games actually rely on pre-B behavior, unlike the MMC3 where it appears no games rely on "old" IRQ behavior.

Author:  3gengames [ Mon Dec 31, 2012 6:54 pm ]
Post subject:  Re: How to detect MMC1 Revisions?

In my testing with my MMC1B2 cart, it always boots in the last bank. I think A and no revision boot in a random state? I know the no revision isn't supposed to. I dunno, I wish somebody who had the ability to quickly test each MMC1 could with my ROM. I can, I just need to socket the MMC1 and desolder a few from a couple donors. I think my kid icarus has a normal MMC1. I have a ton of games, so I should be able find an A and C somewhere.

Author:  Zelex [ Mon Dec 31, 2012 7:01 pm ]
Post subject:  Re: How to detect MMC1 Revisions?

tepples wrote:
Correct me if I'm wrong, but I think MMC1 and MMC1A behave the same: no PRG RAM disable bit. MMC1B has a PRG RAM disable bit but boots in an unpredictable state; MMC1C always boots in disabled state. Only two games actually rely on pre-B behavior, unlike the MMC3 where it appears no games rely on "old" IRQ behavior.


Which two games?

Author:  infiniteneslives [ Tue Jan 01, 2013 12:25 am ]
Post subject:  Re: How to detect MMC1 Revisions?

tepples wrote:
Correct me if I'm wrong, but I think MMC1 and MMC1A behave the same: no PRG RAM disable bit. MMC1B has a PRG RAM disable bit but boots in an unpredictable state; MMC1C always boots in disabled state. Only two games actually rely on pre-B behavior, unlike the MMC3 where it appears no games rely on "old" IRQ behavior.


I believe your correct except for some boards (SNROM) that create a WRAM disable bit with an unused CHR address bit. More of a board behavior than a MMC1 behavior, but it's a behavior that the ROM is subjected to none the less.

Author:  tepples [ Tue Jan 01, 2013 6:39 am ]
Post subject:  Re: How to detect MMC1 Revisions?

Zelex wrote:
Which two games?

tepples wrote:
MMC1A is mapper 155.

The two games believed to require mapper 155 behavior are listed on that page.

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