sigilOS Forge — 75 Systems, SRDX Netplay, Arcade-to-Modern

What sigilOS Forge is

sigilOS Forge (formerly RetroPie) is not an emulator app running on top of Linux. It is a fleet of 75 capability-secured emulator cores running directly in sigilOS as EL0 processes. Each core is spawned with exactly the capabilities it needs — no more:

sigilOS Forge inherits the Four Pillars:

• FAST — near-native dynarec on every applicable core; GPU-first display path (software 2D fallback for Pi 3 1 GB)
• EFFICIENT — Pi 3 / 1 GB is the floor and the target, not an afterthought. Every core is profiled against that ceiling
• SECURE — per-core EL0 isolation; ROM read via CAP_FS_RD only; no ambient authority; a compromised core has no path to the network or to other cores' memory
• STABLE — one crashed core cannot affect other cores or the Lumen WM. Fault boundaries are process boundaries

73 Launchable systems

The full library spans 41 years of video game hardware — from the first consumer video game console to the Nintendo Switch. Every system in the table below is launchable on a Pi 3 with 1 GB RAM.

The ROM library browser

The ROM library browser is built from two Sigil modules: rom_scan.sg and library_scene.sg. The ROM scanner is a Sigil rewrite of the Python equivalent — runs entirely on-device.

Scanner internals: directory listing via fs_readdir (syscall 21) + pure-Sigil CRC32 IEEE 802.3. Policy-compliant: no network calls, no external processes, no ambient FS access outside the ROM library mount. Memory layout:

0x3E000000  CRC table
0x3E030000  ROM entries
0x3E040000  string pool
0x3F000000  scan output

Library scene: 4×5 card grid, L1/R1 system navigation, [dat-verified] badge per dat-matched title, Smart Folder integration — tag any game @retropie, @snes, @favorites, or any user-defined tag, then surface it via the standard Smart Folder query interface.

Savestate ABI — all 73 cores

Commit 1c48e9b (62 files, 730 insertions) extended the savestate ABI to all 73 cores. Previously only 7 cores implemented this interface. Every core now exposes:

core_savestate(slot)        // write state to savestate slot
core_loadstate(slot)        // restore from slot
core_savestate_size()       // return byte size of this core's state

Three implementation patterns cover the full library:

• Old-ABI wrapper (11 cores: coleco, i8080, atari, c64, genesis, msx, pce, sms, sg1000, snes, zx) — thin delegation wrappers over the pre-existing state routines
• Single-region copy (most new cores) — RAM + CPU state lives contiguously before the framebuffer; one memcpy in, one out
• Two-region copy (psx, n64, saturn, dreamcast, and similar) — CPU state lives after the framebuffer; saves two non-contiguous regions to skip the large framebuffer allocation entirely

Savestate sizes by core:

SRDX netplay — Mode-1 and Mode-2

SRDX netplay is the flagship feature of sigilOS Forge. The savestate ABI across all 73 cores exists specifically to enable rollback netplay on every system in the library — from Street Fighter II on SNES to Marvel vs. Capcom 2 on Dreamcast.

Mode-1: pixel stream

The emulator core writes frames to the framebuffer as normal. fbtap.sg intercepts the framebuffer output, srdx_encode compresses the dirty-tile diff, and the SRDX transport (TCP or raw-NIC) delivers the encoded frame to the remote player's sigilOS viewer. The remote player sees a live view of the game with no additional core overhead on the host.

Input from the remote player arrives via the SRDX INPUT message and is injected directly into the core's gamepad ABI — the same interface used by physical controllers. One machine runs the core; the second player sees and controls everything through the stream.

Mode-2: rollback netplay

For fighting games and any latency-sensitive genre, Mode-2 runs a local copy of the core on both machines simultaneously. The SRDX ACPI PM timer (3.579545 MHz, 279 ns resolution) is the authoritative rollback clock shared across the session.

When a late input arrives on either side:

1. Both sides call core_loadstate(snap_slot) to restore the pre-divergence frame
2. Replay advances from that snapshot with the corrected input sequence
3. The session resumes in sync — with no visible interruption on either display

snap() / rest() on all 73 cores makes Mode-2 available for every system in the library. Controller state is saved alongside core state — all 5 supported controllers implement the rollback ABI.

Session logging: the SRDX connection log (srdx_persist_log_join / log_leave / log_count) tracks every active netplay session. Entries are 8 bytes, append-only, with sequence number derived from file size — crash-safe with no WAL required.

Input stack

Four Bluetooth controllers plus GPIO arcade HATs, with a dedicated P2 core bridge. All drivers share the snap() / rest() rollback ABI — controller state is saved with core state in every Mode-2 snapshot. Local two-player is fully wired: core_input_p2.sg routes the P2 Xbox BT slot into the emulator core, and exposes the same core_set_input_p2() function that SRDX Mode-2 uses for remote input injection.

Status