0xrsydn/gameboy-rust
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fix(bios): preserve documented protected-read words at firmware exits

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Place skipped compatibility data at boot, SoftReset, SWI, and IRQ exit PC+8 locations. Preserve the real IRQ callback return instruction as its readback word. Keep CPU and memory behavior image-derived, including caller-supplied images.

Add original boundary, load-lane, caller-state, wait, supplied-image, and builder-fixup regressions. Document the historical failures, research decision, passing public BIOS checkpoint, and remaining fetch-history limits.

Validated on Darwin arm64: 868 workspace tests in debug and release; 799 core/demo tests separately in both profiles; 39 preparation tests; native ROM window tests in both profiles; ten graphics/window smoke modes; fmt, clippy, and rustdoc. Hash-verified public ARM, Thumb, memory, and BIOS suites pass unchanged with identical debug/release reports. BIOS: r12=0, 17606 steps, 197456 nominal cycles, one IRQ entry.
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0xrsydn 2026-10-06 00:37:20 +07:00
commit efdc288db6
15 changed files with 387 additions and 34 deletions
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docs/public-memory-tests.md
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@ -81,7 +81,8 @@ Adjacent halfwords must remain unchanged. Ignored stores still pay their nominal
Halfword and word stores still modify object video RAM and object attribute memory.
These are implementation regressions based on documented rules, not new hardware measurements.
No public BIOS, timing, graphics, save, or unsafe suite is claimed as passing.
The [public BIOS read-protection ROM](public-bios-tests.md) has a separate bounded passing result.
No public timing, graphics, save, or unsafe suite is claimed as passing.
Pokémon Emerald compatibility remains unverified.
## References