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 Post subject: FDS to NES conversion
PostPosted: Tue Jan 21, 2014 11:05 am 
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A little question: Is converting a Famicom Disk System ROM to an NES cartridge ROM complicated and something that has to be adjusted individually for every game or is this a task where the algorithm is the same for every game, so that it can be done automatically by a program?

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PostPosted: Tue Jan 21, 2014 11:09 am 
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Complicated : Not if you have the source code of the program and can easily recompile/link it differently.
Otherwise, yes it is and no you can't do an automatic conversion.


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PostPosted: Tue Jan 21, 2014 11:18 am 
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I imagine you could construct a mapper that made the process totally automatic. It would have:

8KiB SRAM @ PPU $0000
32KiB SRAM @ CPU $6000
8KiB ROM @ CPU $E000 -- your custom boot rom

It would need to have all of the BIOS entry points correspond to actual FDS bios entry points, and emulate all of the FDS IO regs that programs use. It would then copy data into the VRAM or WRAM sections from an internal ROM, with data bytes appearing on $4031, just like the real system did.

Or better yet, you could use actual FDS hardware and just make custom stuff to replace the disk drive itself, which communicates with the FDS through a very simple serial interface.

Either way would be much more expensive to manufacture than hacking apart the ROM image and making it work with a simpler mapper.

In some of the FDS pirate carts out there (EG iNES mappers 40, 42, 50), you do see memory arrangements that sort of mimic the real thing and code with minimal changes in it. But they still had to do some manual patching of the program code.


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PostPosted: Tue Jan 21, 2014 12:57 pm 
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natt wrote:
It would need to have all of the BIOS entry points correspond to actual FDS bios entry points, and emulate all of the FDS IO regs that programs use. It would then copy data into the VRAM or WRAM sections from an internal ROM, with data bytes appearing on $4031, just like the real system did.
And we'd call it a powerpak! ;)
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Or better yet, you could use actual FDS hardware and just make custom stuff to replace the disk drive itself, which communicates with the FDS through a very simple serial interface.
The bitrate of the FDS is 75kbit or so (after all, 65kB/side / 7 seconds) so this is fakeable using a microcontroller. But 1- it's not like the original 2C33 is all that widespread: the market is very small among people who will be reading this thread, and 2- the .fds format doesn't store the exact contents of the disks, so they'd need to be massaged back.
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Either way would be much more expensive to manufacture than hacking apart the ROM image and making it work with a simpler mapper.
Yup!


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PostPosted: Tue Jan 21, 2014 1:21 pm 
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lidnariq wrote:
natt wrote:
It would need to have all of the BIOS entry points correspond to actual FDS bios entry points, and emulate all of the FDS IO regs that programs use. It would then copy data into the VRAM or WRAM sections from an internal ROM, with data bytes appearing on $4031, just like the real system did.
And we'd call it a powerpak! ;)
Quote:
Or better yet, you could use actual FDS hardware and just make custom stuff to replace the disk drive itself, which communicates with the FDS through a very simple serial interface.
The bitrate of the FDS is 75kbit or so (after all, 65kB/side / 7 seconds) so this is fakeable using a microcontroller. But 1- it's not like the original 2C33 is all that widespread: the market is very small among people who will be reading this thread, and 2- the .fds format doesn't store the exact contents of the disks, so they'd need to be massaged back.
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Either way would be much more expensive to manufacture than hacking apart the ROM image and making it work with a simpler mapper.
Yup!


That second proposal of mine seems much better suited for some sort of "backup" system to allow owners of an FDS to play their games with quicker load times and without putting wear and tear on physical disks.


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PostPosted: Tue Jan 21, 2014 5:50 pm 
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If you want to convert one specific game from FDS to a different mapper, depending on the game you may be able to use a very simple mapper. It's just that this is not an automatable process. It really depends what your goal is, here.


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PostPosted: Wed Jan 22, 2014 12:02 am 
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Many FDS-games stores variables/data in $6000-$DFFF addressrange which is a showstopper for NES-conversions since we're only allowed to have PRG-ROM at these locations (except if using MMC5, which I know someone have ported FDS-Doki Doki Panic).

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PostPosted: Sun Dec 17, 2017 3:33 am 
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Someone will be able to convert Aliens, the fds prototype?

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PostPosted: Sun Dec 17, 2017 4:06 am 
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natt wrote:

That second proposal of mine seems much better suited for some sort of "backup" system...

If I remember correctly something like this already exists, and is called Fds stick.
I don't know how good it is.
But nothing stops you or anybody to try to do something similar.


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PostPosted: Sun Dec 17, 2017 7:01 am 
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lancuster wrote:
Someone will be able to convert Aliens, the fds prototype?

Did you seriously necro-bump a three years old thread about a general topic just to ask whether someone can convert a specific game for you?

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PostPosted: Sun Dec 17, 2017 7:03 am 
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Fisher wrote:
natt wrote:

That second proposal of mine seems much better suited for some sort of "backup" system...

If I remember correctly something like this already exists, and is called Fds stick.
I don't know how good it is.
But nothing stops you or anybody to try to do something similar.
It exists and it's great. I can't really find any flaws on the FDSStick for what it is. It didn't exist back when the quoted post was created though.


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PostPosted: Sun Dec 17, 2017 10:15 am 
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Sorry, my mistake!!
I should pay more attention on the dates before posting... :oops:


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