This project boots the real Philips CD-i system ROM as native code and can run the early stages of Hotel Mario through the real OS-9 drivers. Normal-speed input has cleared Hotel 1 Stages 1–3, reaching Stage 4. Full campaigns, bosses, the ending and correct save restoration remain unverified. Expect rough edges, missing features, incomplete hardware coverage, and breaking changes. This is a research project shared in the open, not a finished product — and it is a static recompiler, not an emulator.
cdirecomp is a static recompiler for the Philips CD-i. It lifts the console's Motorola 68000-family machine code (CPU: SCC68070) into portable C, then links that generated C against a hand-written runtime that re-creates the rest of the machine — the MCD212 video decoder, the CDIC / CIAP CD + XA-audio path, and the SLAVE / IKAT input controller — and runs the console's CD-RTOS / OS-9 operating system on top.
It shares the two-tier structure and spirit of the sibling projects
nesrecomp, snesrecomp, segagenesisrecomp, and
psxrecomp.
Real CD-RTOS player shell · Time/Date settings · the Philips Interactive Media bumper · and Hotel Mario reaching its title card through the real recompiled system ROM.
The guiding inspiration for cdirecomp is to be LLE (low-level emulation) and static / native-first:
- Low-level, not HLE. There is no hand-written OS-9 HLE layer. The whole
CD-RTOS system ROM is recompiled and executed as native C. A game's
TRAP #0OS-9 system calls dispatch into the recompiled kernel, and kernel state lives in emulated RAM exactly as it does on hardware. Only the hardware chips are modeled by hand. (psxrecomp showed that stubbing the BIOS leads to silent failure; CD-i takes the opposite, faithful route.) - Static, not interpreted. The 68000 code is translated ahead of time to C and compiled to a native binary. A clean-room interpreter is kept only as the correctness floor for RAM-resident / not-yet-statically-promoted code.
The Genesis runs a bare-metal 68000 cartridge; CD-i does not. A CD-i title
is a Green Book Mode-2 CD whose data track holds a CD-i/ISO-9660 file
system. The program is a set of OS-9/68000 relocatable modules (sync word
0x4AFC) that CD-RTOS — a real-time OS based on Microware OS-9/68K — loads
and relocates into RAM at run time, reaching the system through TRAP #0
system calls. So cdirecomp recompiles and executes the whole player system
ROM first, then lets the game boot on top of it.
What works today:
- Boots the real CD-RTOS system ROM (user-supplied) to its interactive player shell — navigation, the Time/Date and storage settings UIs, media insert/eject, and persistence — running as native recompiled code.
- Hotel Mario boot and early gameplay. From the shell you can Play CD-I a user-supplied Hotel Mario (USA) disc; CD-RTOS loads the title, the Philips Interactive Media bumper plays with decoded XA audio, and the game reaches its title card and one-player gameplay. Intro background changes now follow the disc's file-wide trigger events. Windowed input and buffered XA playback reach gameplay through the real OS-9 drivers. Normal-speed controller input cleared Hotel 1 Stages 1–3 on the indexed LLE build. A separate seeded two-player build reached Stage 3 for Mario and Stage 5 for Luigi. These are partial playthrough observations using ordinary game input.
- Owner playtest feedback (2026-10-09). Basic gameplay and the title-screen background are reported working well. Minor visual flickering remains; its cause has not been investigated.
- Static native OS-9 modules. The disc frontend validates file extents, header parity and CRC, then emits relocatable C with instruction resume maps. Hotel Mario supplies 174 distinct executable images. The runtime binds a loaded image by its full SHA-256 and revokes that binding on overlapping RAM writes. Uncovered code uses the clean-room interpreter. An indexed, bounded coverage ledger retains executed offsets for offline promotion.
- Recorded checks. All six compiler and eleven runtime component checks passed. The latest indexed build passed 30/30 normal-speed headless cold boots to the exact title; the preceding build also passed 30/30 windowed boots. The latest windowed batches ended early and remain failed.
- Original-game persistence observed. A named save survived a normal window close and appeared in the restore menu after a cold boot. Restoring the correct active stage still needs validation.
- Real-time clock (RTC) on Windows. The runtime can seed the CD-i's DS1216 real-time clock from your Windows host clock once at startup (opt-in), and the player's on-screen Time & Date settings screen is functional.
- Working mouse control on Windows. The host mouse drives the CD-i pointer directly through the runtime's IKAT input model — including inside Hotel Mario, not just the shell.
- Clean-room device models for the MCD212 video pipeline (bitmap, CLUT, RGB555, DYUV, RL7/RL3, mosaic, transparency/matte compositing, cursor), the CDIC/CIAP CD + XA audio path, and IKAT input — rewritten from hardware documentation, with an optional local emulator used only as a black-box behavioral comparator during development.
What is not done yet:
- Minor visual flickering, reported during the owner's manual playtest and
tracked as
beads-ssy9.1. - Full-playthrough certification remains open. All hotels, bosses, campaign cutscenes, both complete player modes and the ending need legitimate input-driven validation. Earlier stream-restart and death/restart failures were corrected, but three complete attract circuits are not yet certified: older long runs overflowed their coverage capture, and the latest DirectSound run ended before its required capture.
- Current windowed reliability, audio and performance acceptance. The latest windowed cold-boot batches exited before completion. Long gameplay also recorded PCM drops with SDL's dummy consumer. Audio listening quality and sustained real-time performance remain unverified.
- Save restoration and release acceptance. Fresh Hotel Mario v0.0.2 Windows ZIP and Linux AppImage packages passed packaging audits and short normal-speed boots to the exact title screen. These preview builds include the indexed coverage ledger; complete campaigns remain unverified.
- Broader title compatibility beyond the current Hotel Mario bring-up.
- Unexercised I2C/MMU paths and additional exception cases remain platform backlog, driven by real applications as they are brought up.
The 2026-10-09 checkpoint is committed for default-branch integration. Gameplay implementation and campaign probes remain paused. LLE is the default; no HLE was added in this work.
See ISSUES.md for the tested/untested matrix, exact build identities,
evidence paths, Beads references and resume notes. TODO.md, PLAN.md, and
BIOS-CLOSEOUT.md cover the roadmap and BIOS/player-shell milestone evidence.
cdirecomp ships no copyrighted material — no BIOS ROM, no disc images, and no game-derived generated code. To run anything you must provide, from your own legally dumped media:
- A CD-i player system ROM (e.g. a 512 KiB
cdi490a.rom). - A CD-i title as a raw Mode-2
.cue+.binimage.
Toolchain: CMake + a C11 compiler + the SDL2 development package. Builds with Visual Studio 17 2022, and is also verified with MinGW gcc + Ninja.
# Recompiler (CdiRecomp) — 68000 frontend + CD-i disc/module inventory
cmake -S recompiler -B build/recompiler -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build/recompiler -j
# Recompile the CD-RTOS system ROM to C (emit generated BIOS)
build/recompiler/CdiRecompBios.exe bios/cdi490a.rom --emit
# Recompile Hotel Mario's executable OS-9 modules from your own disc.
# named-offset32 explicitly opts into this game's Subr export-table layout.
build/recompiler/CdiRecomp.exe "path/to/Hotel Mario (USA).cue" --emit --out hotelmario/generated --subr-exports named-offset32
# Runtime (CdiRuntime) — hardware models + native/interpreted guest execution
cmake -S runner -B build/runner-release -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build/runner-release -j# Inventory a CD-i disc: tracks, volume descriptor, OS-9 modules
build/recompiler/CdiRecomp.exe "path/to/Game (Region).cue"
# Boot the user-supplied system ROM to the player shell
build/runner-release/CdiRuntime.exe bios/cdi490a.rom
# Boot with a Mode-2 disc mounted; click "Open" then "Play CD-I" in the shell
build/runner-release/CdiRuntime.exe bios/cdi490a.rom --disc "path/to/Game.cue"Controls: the mouse moves the CD-i pointer (and clicks its buttons);
arrows/WASD also move it; Enter/Space/Z is button 1; Backspace/X is button 2;
F11 or Alt+Enter toggles fullscreen; Esc exits. A standard game controller maps
D-pad/A/B. Dropping a .cue/.bin onto the window mounts media live.
A normal run creates player.cfg in SDL's per-user preference folder (its path
is printed at startup). Two opt-in preferences, both off by default:
[input]
capture_mouse = true ; hide + capture the host cursor while focused
[rtc]
sync_host_on_startup = true ; seed the CD-i clock from host time once at bootcapture_mouse maps relative host-mouse motion and the left/right buttons to
the CD-i pointer and buttons 1/2; focus loss or Esc releases it immediately.
sync_host_on_startup copies host-local time into the DS1216 only before the
first guest instruction — it never continuously re-syncs. A normal run also
maintains nvram.bin (the DS1216's battery-backed SRAM) beside player.cfg.
The 68000 frontend descends from the author's own segagenesisrecomp; the CD-i
device models are clean-room rewrites from hardware specifications. No
third-party emulator source is used in the recompiler or runtime. An optional
CeDImu checkout may be used locally as a black-box behavioral oracle only — it is
git-ignored and never committed, packaged, or required. See PROVENANCE.md and
THIRD-PARTY-NOTICES.md (SDL2).
PolyForm Noncommercial License 1.0.0 — © 2026 Matthew Stan. This license covers the cdirecomp source only. It grants no rights to any Philips, Nintendo, or other third-party intellectual property; you must supply your own legally obtained system ROM and disc images.
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