M68 mini retro console

Notes and tooling from reading the SD card of a retro TV game stick sold as an SJGAM M68 (build M68 V1.0.0, 22 January 2026) — a clone of the SJGAM M66.

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History

It is not an M66. It is a clone of one: the M66's casing, photographs and product page around a cheaper board running entirely different software. SJGAM's catalogue has no M68 in it, because the M68 is not one of their products — so the specification on the page it is sold under (Amlogic-class SoC, Mali-G52, EmuELEC 4.3) is the specification of the device being copied. Set side by side:

	M66, as listed	This unit
CPU	Amlogic-class, Mali-G52 MC2	Rockchip, 32-bit ARM Cortex-A7
OS	EmuELEC 4.3	Buildroot 2018.02-rc3, BusyBox init
Interface	(EmulationStation)	MiniGUI, /usr/bin/game
Emulation	"30+ emulators"	RetroArch, 26 of 37 referenced cores present

The emuelec/ and emulationstation/ directories in the root filesystem are empty mount points — the layout copied over without the software behind it.

Nothing published describes this board, so the rest of this came off the card:

• The menu is a directory listing. Categories come from readdir("/sdcard/game"), capped at 50. mkdir is the whole procedure for adding a system.
• /sdcard/game1 is a dead end. The launcher scans it every boot, but tags the rows with a path no category tile matches. Put ROMs in /sdcard/game/<system>/ and build games.db for them (below).
• 720p50 is a script's choice, not a hardware limit. drm-hotplug.sh prefers 1280x720 over 1920x1080, and the mode is matched on size alone, so the refresh rate is whichever the TV lists first. 1080p can be forced from test.sh; on our unit it worked but flickered and looked no better, so stock stays.
• /sdcard/test/test.sh replaces the launcher, checked for by S50ui at boot. No firmware modification, fully reversible.
• /etc/webster is decrypted. It turned out to be an older start_game.sh. The cipher keys off a window of the init script XORed with the kernel builder's user@host — a tamper check rather than a secret. It is stale, and the code that reads it is unreachable, along with a Rockchip eFuse anti-clone check.
• Nine menu icons have no emulator behind them (dreamcast, naomi, cps3, nds, …).

Layout

NOTES.md                      the full teardown: boot path, menu, schema, crypto, addresses
webster-decrypted.sh          plaintext of /etc/webster
games.db, games_scanf.db      the shipped SQLite databases (21,520 rows)
games_fav.db                  favourites
tools/                        see below
assets/                       product photograph from the M66 listing
squash/                       extracted root filesystem (gitignored — ~460 MB)

Tools

tools/build_gamesdb.py — build or extend games.db

tools/build_gamesdb.py scan   ROMDIR                        # dry run, flags missing cores
tools/build_gamesdb.py build  ROMDIR -o games.db --base games.db
tools/build_gamesdb.py titles games.db -o titles.csv        # edit, feed back with --titles

ROMDIR holds one directory per system (ROMDIR/snes/Foo.zip). Rebuilding with --base reproduces all 21,520 stock rows byte-identically before appending.

Warning

The launcher loads titles with a bare SELECT en_title FROM tbl_en — no WHERE, no ORDER BY — and indexes the result positionally against tbl_game. The en_id/zh_id/ko_id/tw_id columns are never joined on. Every title table must have the same row count as tbl_game, in the same order, or every title after the gap shifts onto the wrong game. The script asserts this before writing.

Starting from scratch with your own ROMs

A category tile is a directory in /sdcard/game, and it lists exactly the rows whose timer is /sdcard/game/<that directory>. So the ROMs and games.db must both live under /sdcard/game:

1. Lay out roms/<system>/<file> on the PC, using the firmware's folder names (snes, md, cps, gba, … — see NOTES.md).
2. tools/build_gamesdb.py scan roms — check every folder maps to a core that ships.
3. tools/build_gamesdb.py build roms -o games.db — no --base, so no stock rows.
4. Back up the card's /sdcard/game, then delete its system folders and .db files.
5. Copy roms/* into /sdcard/game/, plus the games.db from step 3 — check sqlite3 games.db "select count(*) from tbl_game" isn't 0 first. Don't copy games_fav.db or games_scanf.db; the launcher creates both at boot.
6. Leave /sdcard/game1/* empty.

What game1 is: every boot the launcher copies games.db to games_scanf.db and appends a row for each file under /sdcard/game1/<system>/, with timer = /sdcard/game1/<system>. No tile ever matches that path, so from the code those games are not listed under any category. Earlier versions of this README recommended game1; that was wrong. Leave its folders empty (the launcher recreates them at boot).

tools/make_blank_dbs.py — empty databases

tools/make_blank_dbs.py OUTDIR      # OUTDIR/games.db, OUTDIR/games_fav.db; --force to overwrite

Same schema as stock, no rows. Not needed for setting up a card — the launcher creates games_fav.db itself — and its games.db is empty: copied to a card, every tile shows nothing.

tools/make_test_launcher.sh — replace the launcher

tools/make_test_launcher.sh [-t lvui|game|retroarch|shell] [-m WxH] [-n] /Volumes/SDCARD

Writes the /sdcard/test/ override. Logs each boot to the card, and falls back to the stock launcher if the target dies within 15 s, so a failed experiment can't leave a black screen with no way back in. Run -t game first to prove the hook fires.

-m 1920x1080 forces the HDMI mode (see below) and logs the TV's mode list to test.log.

tools/webster.py — the encrypted blob

tools/webster.py params                                     # what a rootfs derives
tools/webster.py decrypt squash/etc/webster -o webb.sh
tools/webster.py crack   squash/etc/webster --model squash/usr/local/share/minigui/start_game.sh

crack recovers size, offset and key from scratch without /proc/version.

HDMI mode

S50ui runs /usr/bin/drm-hotplug.sh, whose preference list is 1280x720 1024x 1280x1024 800x600 1920x1080. It writes the winner as a bare WxH to /tmp/drm_mode.cfg, which MiniGUI and the vendor RetroArch both read, taking the first TV mode of that size. 720p50 and 720p60 share a pixel clock, so the TV's EDID order decides the refresh rate — hence 50 Hz on some sets.

tools/make_test_launcher.sh -t game -m 1920x1080 CARD overrides it without touching the rootfs (the UI still draws at 720p and is scaled). Tried on one unit: 1080p came up, with some flicker and no visible gain, since everything on screen is upscaled anyway. Delete /sdcard/test to go back.

Licence

The work in this repository is MIT licensed — tools/, NOTES.md and README.md.

The MIT grant does not extend to the material that came off the device or from the SJGAM listing, which is included for reference and remains its rights holders':

No reuse licence was established for any of those. Attribution does not grant permission for redistribution.