I'm in the process of building a replica personality module for the SOL-20 using 4 MM5204's.

I have inspected the dump of a solos that came on a disc with a replacement personality module from ebay and also I have dumped another personality module's contents from another version of the module. These dumps match, indicating they are probably correct/normal.

However, I got a little surprise when I dumped the contents of my Sol's original module with the 4 MM5204's, it does not match, The final byte at C7FF which is an FA for the other dumps, is an 00 in my MM5204 module. All other bytes are a perfect match.

Can anyone suggest:

1) how this could have come about, if it is rom rot, would it go to FF or 00 for this IC ?
2) what would be the implication/result of that last byte of the Solos file being incorrect ?