> Is it possible that the high-end programmer can descramble the data?
> OTOH is the scrambling process lossy? If it is not, it is possible to
> recover the original data :-(.

The scrambling process consists in XORing all three nybbles of each ROM
location with each other and masking off the upper two nybbles. Maybe
Andrew Warren knows about a more recent mask revision, I still use 16C54
and 16C54A CERDIP for development (from 1995!). The only thing that does
not work anymore is the writing on the chips so I had to scribe them with
a needle. Everything else works fine ;-).

Peter

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