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!