Two diagnostic experiments while chasing the divide-by-zero break from the
previous commits (see docs/VSHBootInvestigation.md "Attempt 8"/"Attempt 9"):
- Unregistered MMIO reads now return a distinctive poison value
(0x1337BEEF) instead of 0, so a future trace can tell at a glance when a
value traces back to an unimplemented register instead of looking like an
ordinary zero.
- COP0 register 9 (Count) now returns a live CoreTiming-derived value
instead of a static shadow-array read, matching how real hardware free-
runs it regardless of software writes.
Neither change altered the reboot.bin free-run's outcome at all (identical
break, same PC) - ruling out both as the source of the zero divisor traced
in the previous commit. Kept anyway: both are straightforwardly more
correct/useful than what was there before, independent of this specific
bug.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GZq8ZtJmFY7bkX5FVkr3P9
(cherry picked from commit ac446449d9031b628d7d9c4dbc101638840f8434)
Henrik Rydgård
0c7f8ca07c