Upgrading a Microbee PC85 to a PC85b and adding extra Game ROMs.

[someone]

I suspect more like a signature byte, I think the boot-up to the SHELL menu is too quick to do a CRC check on each ROM every time it boots up.

PS. Even though Self Test doesn't show PAKs 6, 7, 14 & 15 PC85 still checks for and will display in the full menu list, even PAK's 6, 7, 14 & 15.

The only one it will not display is Pak 10 which is reserved for the Menu expansion of SHELL.

Ernest

The first byte is a 0xC3 & checksum is only on the first 256 16 bit words of a PAK ROM so it is done very quickly.
The titles of the recognised ROMS are stored in the menu system; the original PC85 menu and PC85b have slightly different entries.