> Unfortunately, MPSIM will show all your registers as having "00" (except for
> Registers which are initialized on Power Up), so it makes it hard to find.
> In reality, RAM Registers actually power up to some non-zero value.

When trying to debug stuff using "real" chips, I'll write code to ensure
that all the registers are initialized to zero via loop but generally I'll
try to avoid relying on that: for testing I'll make my init-loop initialize
the memory with other junk to ensure the system 'still' works.