You could put microprobes on the die and read out the ROM contents electrically, but that would be difficult and would need specialized equipment. Reading out t

You could put microprobes on the die and read out the ROM contents electrically, but that would be difficult and would need specialized equipment. Reading out the ROM visually is much easier, and there is software that can interpret images if they are clear enough, e.g. maskromtool: https://github.com/travisgoodspeed/maskromtool https://github.com/travisgoodspeed/maskromtool The Pentium's built-in self test is somewhat documented: you pull the INIT pin high while the RESET pin goes low to trigger the test. You can also execute the RUNBIST instruction through boundary scan. I don't think this helps you get the ROM data; the test just reports pass/fail.