Hi,
As many have said before, by 1987 semiconductor ROM sizes were as large as 128KB, and that was the equivelant to both sides of an FDS disk image. This has been the suggested reason as to why the FDS was dropped from Nintendo's product line, despite having its own awesome extra sound channel generator hardware, that I think beats the 2A03's DMC shortcomings by a considerable measure.
However, there is probably more to this story. As usual, Nintendo tries to go to a lot of trouble to protect their systems from 3rd party developers (as can be witnessed with the CIC/10NES program present on the NES and carts). The FDS also came with a number of physical, electrical, and software lock-out schemes that tried to keep hackers out (i.e., Hacker International).
When an FDS disk boots, the ROM BIOS looks for the name table file "KYODAKU", which just contains a copyright notice that the BIOS verifies and scrolls up on the screen, before the actual FDS game is booted up. No KYODAKU file = BIOS returns an error message.
Despite Nintendo's efforts to put the lock and key on FDS development, they seemingly allowed for the game's NMI handler to be enabled by default during the disk boot process. So, all the game has to do to get NMI control (before the BIOS checks KYODAKU after the disk is read), is contain just a one-byte file at the end of the disk, that writes one single byte to $2000 to enable NMI's (plus waste some extra time with dummy disk reading to wait for the PPU's first VINT), and consequently circumvent the ROM BIOS's test for KYODAKU!
You would think that this very minor issue could have been something easily fixable by Nintendo with a revision of their ROM BIOS, but when you consider the fact that Nintendo actually expected developers to call their BIOS disk routines @ hard-coded addresses in ROM, it's no wonder why they couldn't make changes to it. Personally, they should've taken advantage of the BRK #xx opcode to make any 1 of 256 BIOS system calls possible, but nevertheless, I'm sure one of the FDS ROM BIOS developers must have lost their shirt over this little back door.
As many have said before, by 1987 semiconductor ROM sizes were as large as 128KB, and that was the equivelant to both sides of an FDS disk image. This has been the suggested reason as to why the FDS was dropped from Nintendo's product line, despite having its own awesome extra sound channel generator hardware, that I think beats the 2A03's DMC shortcomings by a considerable measure.
However, there is probably more to this story. As usual, Nintendo tries to go to a lot of trouble to protect their systems from 3rd party developers (as can be witnessed with the CIC/10NES program present on the NES and carts). The FDS also came with a number of physical, electrical, and software lock-out schemes that tried to keep hackers out (i.e., Hacker International).
When an FDS disk boots, the ROM BIOS looks for the name table file "KYODAKU", which just contains a copyright notice that the BIOS verifies and scrolls up on the screen, before the actual FDS game is booted up. No KYODAKU file = BIOS returns an error message.
Despite Nintendo's efforts to put the lock and key on FDS development, they seemingly allowed for the game's NMI handler to be enabled by default during the disk boot process. So, all the game has to do to get NMI control (before the BIOS checks KYODAKU after the disk is read), is contain just a one-byte file at the end of the disk, that writes one single byte to $2000 to enable NMI's (plus waste some extra time with dummy disk reading to wait for the PPU's first VINT), and consequently circumvent the ROM BIOS's test for KYODAKU!
You would think that this very minor issue could have been something easily fixable by Nintendo with a revision of their ROM BIOS, but when you consider the fact that Nintendo actually expected developers to call their BIOS disk routines @ hard-coded addresses in ROM, it's no wonder why they couldn't make changes to it. Personally, they should've taken advantage of the BRK #xx opcode to make any 1 of 256 BIOS system calls possible, but nevertheless, I'm sure one of the FDS ROM BIOS developers must have lost their shirt over this little back door.