0xrsydn/gameboy-rust
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fix(memory): ignore CPU and DMA writes to the Game Pak ROM windows

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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
This commit is contained in:
0xrsydn 2026-10-14 08:26:03 +07:00
commit 258fbff2fa
25 changed files with 86 additions and 74 deletions
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7
crates/gba-core/tests/bios/bit_unpack.rs
View file

@ -361,10 +361,10 @@ fn truncated_descriptors_and_sources_return_memory_diagnostics() {
}
#[test]
fn destination_failure_preserves_completed_word() {
fn destination_failure_follows_an_ignored_rom_word() {
let (mut m, _) = prepare(
false,
0x07ff_fffc,
0x0cff_fffc,
&[0x12, 0x34, 0x56, 0x78, 1, 2, 3, 4],
8,
8,
@ -372,9 +372,8 @@ fn destination_failure_preserves_completed_word() {
);
assert_eq!(
fail(&mut m),
MachineError::Cpu(MemoryError::ReadOnly(ROM_START).into())
MachineError::Cpu(MemoryError::ReadOnly(0x0d00_0000).into())
);
assert_eq!(m.memory().read32(0x07ff_fffc).unwrap(), 0x7856_3412);
}
#[test]