Like S80_UK, I also looked up the Holtek part number.  I find it difficult to believe that the board really has an OTP device fitted, with no ability to erase.  However, I also discover that the device went out of production in March 2007 (EOL announced June 2006).

You've been so patient over the last however long. Much thanks to you, and the others who have chimed in as well.

 

Maybe someone else will find the thread and not have any of the anxiety I had.

 

Thanks.  I am only sorry that it didn't work out.  As I said, with a little luck, another SIL3114 controller would either not need an update, or would be able to be updated.  But perhaps we all need to regain our strength, patience, and put back the hair that we've torn out before trying again...