Edit: Job done: See post #2 for the attachment, it's tested & working by Dbstallman
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I took a closer look at DBZVRVS today, and I did not see any big roadblocks.
The custom fd1149 seems to set up a mirror range. When writes to an address occur, they appear at another place in fd1149 ram automatically.
Dbstallman reported that the game will boot with a dead custom. Not without it. This is probably because the game will then hang on writes. There is no shared ram to write to.
With a dead custom several gfx areas are just black. This would happen since the main cpu expects to read back a value from shared ram. The value is always 0 with a dead custom.
I need to look at the game a little bit closer to see where these writes and reads occur. It might be possible to map them to the same address to allow the game to function again with a dead module. Or map them to normal ram to get rid of the fd1149 completely.
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I took a closer look at DBZVRVS today, and I did not see any big roadblocks.
The custom fd1149 seems to set up a mirror range. When writes to an address occur, they appear at another place in fd1149 ram automatically.
Dbstallman reported that the game will boot with a dead custom. Not without it. This is probably because the game will then hang on writes. There is no shared ram to write to.
With a dead custom several gfx areas are just black. This would happen since the main cpu expects to read back a value from shared ram. The value is always 0 with a dead custom.
I need to look at the game a little bit closer to see where these writes and reads occur. It might be possible to map them to the same address to allow the game to function again with a dead module. Or map them to normal ram to get rid of the fd1149 completely.
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