From: nick.westgate@gmail.com   
      
   On Tuesday, February 8, 2022 at 10:17:46 AM UTC+10, awanderin wrote:   
   > Well, there are some vague clues:   
   >   
   > 1. Apple IIgs Firmware Reference, page 281, last line:   
   >   
   > C02C:00 246 CHARROM DFB 0 ; Addr for tst mode read of character ROM   
      
   Wow, great finds, Jerry! I didn't even bother checking the manuals, but those   
   are actually pretty specific clues!   
      
   Funnily enough, another commenter pointed out exactly this use case:   
   "One reason for a back door could be that it enables self-test/diagnostic   
   software to check the function of the ROM and its data paths. If the back door   
   hardware is cheap, that reduces manufacturing cost by simplifying QA."   
      
   Cheers,   
   Nick.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)