258fbff2fa
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
104 lines
5.3 KiB
Markdown
104 lines
5.3 KiB
Markdown
# Local Emerald visible-progress probe
|
||
|
||
## Method
|
||
|
||
A temporary host driver uses public core APIs (deleted after use; lives
|
||
outside version control). It boots the local user-supplied ROM with
|
||
`bios::boot`, selects `CartridgeHardware::Rtc` and `SaveDevice::Flash128`,
|
||
fixes the RTC to `[24, 1, 1, 1, 12, 0, 0]` without advancing it, enables
|
||
scanline rendering, and calls `Machine::run_until_vblank(400000)` once per
|
||
frame. Input snapshots apply after each VBlank capture, before the next
|
||
machine step. Frames dump as checksums plus a final PPM for visual reading.
|
||
No ROM bytes, screenshots, or extracted code are committed.
|
||
|
||
Three schedules were used:
|
||
|
||
- No input (attract mode).
|
||
- `advance`: periodic A/Start taps (A for 10 of every 120 frames, Start for
|
||
10 of every 120 frames offset by 60) to walk through title, menu, and
|
||
dialogue.
|
||
- `sweep`: deterministic rotation holding each button 20 frames in turn.
|
||
|
||
## Observed visible progress
|
||
|
||
No-input attract mode renders the title screen, the Pokémon logo, the
|
||
NEW GAME / OPTION menu, the Prof. Birch scene, and legible dialogue text
|
||
(`Hi! Sorry to keep yo`, `Welcome to the world of POKéMON!`). Menu and
|
||
dialogue text, the Birch sprite, and the spotlight composite correctly.
|
||
|
||
The `advance` schedule reaches further: Birch dialogue, the `And are you?`
|
||
gender prompt, and — at 12,000 frames — the in-game start menu (`BAG A SAVE
|
||
OPTION EXIT`) over the overworld with the player sprite in a room. Frame
|
||
checksums evolve continuously through the run; PC samples alternate between
|
||
the `0x080008c6–0x080008cc` wait loop and game code (`0x082e6dcc`,
|
||
`0x082e6dce`).
|
||
|
||
The `sweep` schedule changes captured output per input (input-dependent
|
||
execution) but its denser presses stall the intro on a blue field; raw
|
||
button rotation is worse than sparse taps for menu progress.
|
||
A 40,000-frame `advance` run completed with exit status zero: no diagnostic
|
||
through frame 39,999, so the reported `INVALID_ARGUMENT_TRAP` at 37,101
|
||
captured frames did not reappear on this input path. Blind taps take a
|
||
different menu path than manual play, so the identical starter-selection
|
||
scene is not confirmed visited — this validates forward progress and no
|
||
regression, not the exact user scenario.
|
||
From about frame 9,000 onward the captures cycle among three checksums
|
||
(`0x24bdf6c568`, `0x2503d09807`, `0x7983c73704`) with periodic black fade
|
||
frames, consistent with Start taps toggling the overworld start menu; the
|
||
scene past frame 12,000 was not visually confirmed. The final frame is
|
||
black mid-fade (checksum zero).
|
||
|
||
Execution is diagnostic-free through 40,000 tapped frames (about 3.9
|
||
billion machine steps). This establishes visible menus, sprite/dialogue
|
||
composition, and input-driven progress — not correct gameplay, audio, or
|
||
saving.
|
||
|
||
## Save-navigation attempt (negative result)
|
||
|
||
A `save-run` schedule replayed the deterministic `advance` path to the
|
||
12,000-frame start-menu state, then pressed Down, Down, A (SAVE), A (YES),
|
||
and A again with settling gaps, running to 13,200 frames with Flash image
|
||
dumps at exit. The run completed without a diagnostic, but the dumped
|
||
131,072-byte image shows no save: bank 0 sectors 0–13 erased, bank 1
|
||
sectors 0–11 programmed with structured non-`0xff` data that does not match
|
||
an Emerald save layout, and the final captured frame is the overworld with
|
||
no save dialog. The pressed menu item was not SAVE (blind taps cannot aim),
|
||
or the dialog timing missed. `save_modified` was not observed true.
|
||
External-game save/restart/load therefore remains unverified and waits on
|
||
manual play with `--save-file`, not on more blind schedules.
|
||
|
||
## Second-game data point
|
||
|
||
A local FireRed ROM (16 MiB) faults during boot init, after about 1.19
|
||
million steps with `--rtc --save-type flash128`:
|
||
|
||
```text
|
||
PC=0x081e37d2 CPSR=0x0000003f System/Thumb
|
||
r0=0x09fe2ffe r1=0x00000020
|
||
read-only memory at 0x09fe2ffe
|
||
```
|
||
|
||
A dynamic trace shows boot code spilling `0x09fe20f8`, `0x04000204`
|
||
(WAITCNT), and `0x09fe2ffe` to the stack, writing `0x1800` to WAITCNT, then
|
||
`STRH r1,[r0]` of `0x20` to `0x09fe2ffe`. That address is ROM window
|
||
`0x09` past the 16 MiB EOF; the bus reports `ReadOnly`. On hardware the
|
||
`0x09` window mirrors `0x08` and ROM writes are ignored. The following
|
||
instruction stream also loads halfwords from `0x09fe20f8`, so reads past
|
||
EOF would fault next under the current policy. Without `--save-type` the
|
||
same ROM faults earlier at `0x0e005555` (`unmapped memory`), i.e. it also
|
||
expects Flash save hardware. Both failures are recorded, not fixed: mirror
|
||
folding plus write-ignore semantics need independent hardware evidence and
|
||
a deliberate policy decision against the explicit-error convention. See
|
||
[the usability roadmap](../usability-roadmap.md) for sequencing.
|
||
|
||
Update: emulated writes to the `0x08`–`0x0c` ROM windows are now ignored, which removes the
|
||
`0x09fe2ffe` store diagnostic. Reads past the end of the image remain explicit errors.
|
||
|
||
## References
|
||
|
||
- [GBATEK memory map](https://problemkaputt.de/gbatek-gba-memory-map.htm):
|
||
three 32 MiB ROM windows at `0x08`/`0x0a`/`0x0c` with wait states 0–2.
|
||
- [mGBA memory at c30aaa8f](https://github.com/mgba-emu/mgba/blob/c30aaa8f/src/gba/memory.c):
|
||
out-of-bounds ROM loads log a game error and return `(address >> 1) &
|
||
0xFFFF`; ROM stores go through patch infrastructure. Precedent for
|
||
non-fatal handling, not a hardware measurement. Not copied.
|