The Disk ][ I/O locations are generally accessed as an offset, using
something like "LDA $C08n,X". However the range from $C080-C08F is
already used for language card in slot 0. SourceGen doesn't have a
way to distinguish between indexed and direct accesses, and even if
it did there's no way to separate one peripheral card from another
without knowing the contents of the CPU register.
As a workaround, the Disk ][ definitions are now in a separate symbol
file. When loaded, the definitions replace the base slot 0 equates.
I figure Disk ][ accesses are more common than language card
manipulation, so I'm making it a default for new projects. Existing
projects that reference the Disk ][ symbols (which existed, but as
constants) will need to be updated to include the new .sym65.
