0xrsydn/gameboy-rust
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feat(memory): retain aligned Thumb BIOS prefetch words

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Snapshot the full word at (executing PC+4)&~3 for Thumb BIOS execution, using strict image reads and incoming instruction state. Keep ARM PC+8 open bus separate and unchanged. Commit snapshots only after successful steps; preserve diagnostic behavior for unavailable lookahead.

Add original regression coverage for both code alignments, load widths and lanes, signed and unaligned values, processor modes, sequential fetches, ARM/Thumb transitions, SWI, RAM-backed POP exits, BIOS boundaries, failure retention, and nominal device progression. Record source evidence and explicit pipeline/hardware-validation limits.

Darwin arm64 validation: 878 workspace tests and 809 core/demo tests in each of debug and release; 39 Python tests; native ROM window tests in both profiles; ten window/graphics smoke modes; fmt, clippy, and rustdoc. Public ARM, Thumb, memory, and BIOS reports match prior passing reports and match between profiles. No physical-hardware validation claimed.
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0xrsydn 2026-10-06 00:57:49 +07:00
commit cb4670c245
12 changed files with 427 additions and 25 deletions
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docs/public-bios-tests.md
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@ -90,7 +90,8 @@ See the [root-cause research](research/bios-readback.md) and [CPU BIOS read-prot
The ARM, Thumb, and memory suites remain separate passing results.
This BIOS result covers boundary readback values, not complete BIOS services, exact fetch history, or commercial-game compatibility.
Thumb BIOS execution, full pipeline behavior, and exact firmware timing remain unverified.
Separate original tests cover bounded [Thumb BIOS snapshots](research/thumb-bios-prefetch.md); this public ROM does not validate that path.
Full pipeline behavior, physical-hardware Thumb readback, and exact firmware timing remain unverified.
## References