Stores to 0x08-0x0c returned ReadOnly and stopped the machine. Hardware ignores
them, and a second game's boot code stores to a ROM mirror. Emulated writes now
pay their bus cost and change nothing. The 0x0d window stays a diagnostic until
EEPROM is modeled there, and host writes stay strict.
Tests that used a ROM store as their failing write now cross an ignored ROM
word into the 0x0d window.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HhfHfHEuzv2AUTd6erW1gU
A core, DMA, rendering, window, or audio error returned before the save was
written, so every completed in-game save since launch was lost. The window now
writes changed bytes on that path too. The diagnostic stays the session error;
a refused or failed write is reported as output. A failed state restore leaves
save memory undefined and is never written. Terminal runs keep the strict rule.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HhfHfHEuzv2AUTd6erW1gU
Machine::save_state and load_state encode the CPU, every RAM, and every device
through Snapshot impls into a versioned, checksummed format. Rejected loads leave
the machine unchanged. The ROM window saves to and loads from one state file
with F5 and F9.
Buffer ARM sequential fetch results and refill target pairs after branches, PC writes, and machine exception entry. Stage advances transactionally, defer speculative fetch diagnostics, and preserve buffered words across CPU/DMA stores and host edits. Add explicit CPU pipeline invalidation for debugger repair and memory rebinding.
Add 15 original instruction-buffer regressions. Keep full-state rollback equality while distinguishing architectural comparisons in semantic tests. Update the display error test for an already buffered branch. Document evidence and separate remaining Thumb, bus-history, and timing work.
Validated on Darwin arm64: 967 workspace and 898 core/demo tests in each debug/release profile, 39 Python tests, native ROM windows, ten window smoke modes, fmt, clippy, and rustdoc. Public ARM/Thumb/memory/BIOS reports and nominal cycles remain unchanged.
