[Updated with corrections]
Someone is guessing that the PC85 & PC85B Menu expects PAKROMS to have specific checksums.
For a PAKROM to be recognised by these menu systems 2 criteria must be met:
A: This checksum is calculated by the sum of the first 256 16 bit words in a PAKROM.
B: The first byte of the PAKROM is 0xC3 for a jump instruction.
If the checksum is not recognised it should appear as a USER ROM.
Some examples.
Space Invaders ROM checksum 0xA8B1 (& first byte 0xC3).
Viatel ROM checksum 0x092E (& first byte 0xC3)
Someone is guessing that the PC85 & PC85B Menu expects PAKROMS to have specific checksums.
For a PAKROM to be recognised by these menu systems 2 criteria must be met:
A: This checksum is calculated by the sum of the first 256 16 bit words in a PAKROM.
B: The first byte of the PAKROM is 0xC3 for a jump instruction.
If the checksum is not recognised it should appear as a USER ROM.
Some examples.
Space Invaders ROM checksum 0xA8B1 (& first byte 0xC3).
Viatel ROM checksum 0x092E (& first byte 0xC3)