rom4x/notes/rom5_zeros.txt

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Inventory of zeros of 5 bytes or more in the IIc Plus ROM
Main Bank
C1FB - 5 bytes
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C4EE - 12 bytes - delete key fix
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C5F3 - 5 bytes
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C6FB - 5 bytes - but Disk II ID here at C6FF
C9A1 - 9 bytes - beep merlin fix part 2
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CFF9 - 7 bytes - ROM 5X switcher
Aux Bank
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C572 - 8 bytes
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C7FC - 7 bytes - ROM 5X dispatch jump at $C7FF
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CE00 - 512 bytes not usable (MIG space)
D3B5 - 75 bytes - Accelerator menu text
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D516 - 234 bytes - ROM 5X boot
D6CE - 306 bytes - ROM 5X misc routines
DB63 - 157 bytes - ROM 5X reset
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DE00 - 512 bytes not usable (second view of MIG)
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F72D - 16 bytes not usable (some kind of data table)
F7ED - 19 bytes
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FB3C - 196 bytes - FBE2 ROM 5X dispatch
- Future: classic beep
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FC3C - 12 bytes
FCC9 - 55 bytes - Accelerator speeds table
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FE96 - 352 bytes - but reserve 65816 vectors
- Accelerator enhancements
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Other potential usable space:
Aux Bank
D249-D32B - 227 bytes
This is the ROM checksum diagnostic, and we currently patch around it
because it fails with the ROM 5X patches in place, for obvious reasons.
We could fix the checksum, or reclaim the space.
To patch around it in a reclaimable fashion, a the JSR instruction at
C53D and the following carry check and JSR must be patched out, easiest
by placing BRA C555 at C53D.