DroidArcadia - RetroBIOS¶
Technical notes
Android build of the Signetics 2650 emulator line by James Jacobs, published as package com.amigan.droidarcadia. A game arrives as a content URI declared by the manifest under MIME type application/octet-stream or application/zip, a zip yielding its first member only, and the read stops at 32768 bytes. This reading is taken from the author's own source archive DroidArcadia-src.rar 4.60, md5 5f88d8b01493a2430d2f9c94da69bf8a, and confirmed against the published DroidArcadia.apk, md5 a72cf2f5e2b213577f3e185aa58f7e21. ref: app/src/main/cpp/da.h:3-5, app/src/main/AndroidManifest.xml:21-37, app/build.gradle:22-28, MainActivity.java:1502-1558, res/values/strings.xml:5-6
Fifteen memory maps over five machines: Interton VC 4000 types A to D, Elektor TV Games Computer basic and expanded, Emerson Arcadia 2001 types G (Emerson), H (Tele-Fever) and I (Palladium), and the coin-ops Astro Wars, Galaxia, Laser Battle and Lazarian (Zaccaria) with Malzak 1 and 2 (Kitronix). ref: android.c:245-261, da.h:445-467
Every ROM those machines run is a const array compiled into libdroidarcadia.so and copied into memory when the machine is set up: a_bios[348] for the Arcadia boot stub, i_bios[287] for the Interton one, e_bios_philips[2048] and e_bios_hobbymodule[2048] for the two Elektor monitor ROMs, galaxia_game, astrowars_game, lb_game and lz_game for the Zaccaria coin-ops, m1_bios and m2_bios for the Malzak pair. The first sixteen bytes of all ten arrays are present in the arm64 library of the published apk. ref: android.c:588-596, arcadia.h:279 with arcadia.c:426, interton.h:1 with interton.c:36, elektor.h:1,131 with elektor.c:95-103, zaccaria.h:1,644,1599,3653 with zaccaria.c:243,325,423,436, malzak.h:1,558 with malzak.c:363,373
The native side never opens a file. It receives the game as a byte array over JNI and parses it in memory: a cartridge is matched on size and CRC32 against the games.h table, and the bios field of the matched entry carries the Arcadia region and picks which of the two Elektor monitor ROMs is installed. RetroAchievements identification is handed that same memory with the file path argument left NULL, so the file reader of the bundled rcheevos is never reached. A coin-op is stepped to through the machine button rather than loaded, and a raw binary aimed at Zaccaria or Malzak hardware is refused. ref: android.c:877-894, android.c:2166-2192, android.c:2082-2096, android.c:1010-1013, android.c:4592-4631, elektor.c:95-103, OptionsActivity.java:455-465
No BIOS or firmware files required.
Why no files
Nothing to obtain. The app reads back only what it writes in its own private storage, each read wrapped in a catch that continues when the file is absent: DroidArcadia.ini for settings, DroidArcadia.hgh for the high score table, and Autosave.cos with Quicksave.cos for save states. Screenshots go out to /sdcard/Pictures/DroidArcadia and are never read back, and RetroAchievements traffic, login and badge and game images alike, is decoded in memory. The apk carries no assets directory and no raw resource, so no payload is unpacked on first run either. ref: MainActivity.java:1123,1184,1242,1312,1340,1415, OptionsActivity.java:224-235,682,742, RAActivity.java:237-238,268-269, NetworkUtil.java:17-38
Generated on 2026-08-23T16:12:06Z