Set Up an ANBERNIC Handheld: Firmware, SD Cards, and Your Own Games

For a dual-slot Linux ANBERNIC XX handheld, the safest setup is to back up the supplied card, install the firmware image made for your exact model on a new microSD card in TF1/SYS, and use TF2/GAME for your own legally obtained games. You do not need to open the device. Keep the factory card untouched as a fallback, and do not download copyrighted games or BIOS files you do not have the right to use.

This guide focuses on the H700-based Linux family, including the RG35XX Plus, RG35XX 2024, RG35XX H, RG35XX SP, RG40XX H and V, RG28XX, and RG CubeXX. Check the name on the back of your unit: similarly named models can use different hardware and firmware. Android models such as the RG406H, RG556, and RG557 need a different setup guide.

What do you need before setting up an ANBERNIC?

Gather the handheld, a charged battery, a computer, a USB microSD reader, and one or two reliable microSD cards. For a dual-slot XX model, plan on one card for the operating system and another for games. A separate spare OS card is useful if you want to compare firmware without disturbing your game library.

• TF1/SYS: holds the operating system on the dual-slot Linux XX family.
• TF2/GAME: holds games and related files, and can be removed to copy files on a computer.
• Card size: Retro Handhelds recommends about 32 GB for custom firmware and at least 64 GB for a games card. Its guidance says stock Anbernic firmware needs a 64 GB TF1 card. For a single-card setup, follow the exact firmware’s current requirements.

Replace the generic card supplied with the handheld rather than trusting it as your long-term setup. Retro Handhelds warns that included generic cards are prone to failure. RetroTechLab names a SanDisk Ultra 128 GB A1 card as ample for an Anbernic XX handheld; a Samsung EVO Select is another named option in Retro Handhelds’ guidance. An A1 application-class card is rated at 1,500 read IOPS and 500 write IOPS; A2 is rated at 4,000 read IOPS and 2,000 write IOPS. Those ratings do not mean an A2 card is required for this Linux handheld. The SD Association figures cited by RetroTechLab are 10 MB/s sustained write for U1/Class 10 and 30 MB/s for U3/V30.

Buy from a reputable seller, and check a new card’s full capacity before relying on it. H2testw is a Windows option; F3 is available for Mac and Linux. This can expose counterfeit cards that claim a larger capacity than they really have. Use a card reader rather than repeatedly inserting and removing TF2 if your model has no Wi-Fi.

How do I identify the right firmware for my ANBERNIC?

Match the image to the full model name printed on the back of the handheld, then confirm that model appears on the firmware project’s device list. Do not choose based only on a similar product name or the fact that two devices look alike.

The H700 family includes the RG35XX Plus, RG35XX 2024, RG35XX H, RG35XX SP, RG35XX Pro, RG34XX and RG34XX SP, RG40XX H and V, RG28XX, RG CubeXX, and related models. An RG35XX Plus image is not a safe substitute for an RG35XX H image or the original 2022 RG35XX image. KNULLI explicitly does not support the original 2022 RG35XX because it uses different hardware. ANBERNIC reuses names across revisions, so check the device itself, not just the name remembered from a shop listing.

Official stock images are organized by model at ANBERNIC’s download page. For community firmware, use the project source and its device list: MustardOS/muOS device downloads or the KNULLI Linux releases. These are different projects; a KNULLI image is not interchangeable with a muOS image.

Do not use an H700 image on higher-end Android models such as the RG406H, RG556, RG557, RG DDS, or RG477M. They have a different software stack. If your model is not listed by the firmware project, do not guess at a close match.

Should I use stock firmware, muOS, KNULLI, or MinUI?

Choose stock for the factory experience and a straightforward recovery option, muOS for a play-first launcher, KNULLI for an EmulationStation-style interface and more configuration, or MinUI for minimal menus and a simple hand-off. These options run on the same H700 hardware, so changing the launcher does not change the handheld’s fundamental emulation ceiling.

Firmware	Interface and fit	Setup and transfer notes	Important caveat
ANBERNIC stock Linux	Factory menus with RetroArch; useful if you want the original experience or a recovery card.	Model-specific image from ANBERNIC; Retro Handhelds says stock requires a 64 GB TF1 card.	Community guides describe it as less polished than custom distros.
Stock OS MOD	Modified stock look with quality-of-life additions, including a self-hosted Game Manager web interface.	Latest version noted by Stock OS MOD documentation is v4.0.4, dated 20261025; flash the model-specific split archive, then upgrade online or offline.	The RG28XX and RG35XX 2024 cannot use its Wi-Fi online updater.
MustardOS / muOS	Play-first menus and a short route from startup to a game.	Current image train listed as 2606.0 Andromeda; dual-card guidance is 16 GB or more for OS and 64 GB or more for games.	Use the current device download and add-content instructions; old build nicknames and screenshots can be stale.
KNULLI	EmulationStation interface, broad configuration, scraping, and installable PortMaster support.	Current stable Anbernic release identified here is Scarab, dated 2026-05-11. The Scarab release includes RetroArch 1.22.2.	Scarab changed the partition table; the project recommends a clean reflash rather than carrying forward Gladiator II system configuration.
MinUI	Minimal game lists and a simple interface; a strong choice for a device you want to hand to someone else.	Its documented setup uses stock OS, dmenu.bin on TF1, and a FAT32 TF2 card with the unpacked package contents.	It follows a different card and file layout from the other custom firmware options.

Version details are time-sensitive. The MustardOS/muOS torrent index lists 2606.0 Andromeda, build db2a3bd0, for the device table. KNULLI’s current stable Anbernic release is Scarab, not the older Gladiator name still shown in some guides. The KNULLI project describes itself as a custom firmware developed as a fork of Batocera. Mainline Batocera is not the image to flash on an H700 XX handheld; community coverage reports that it does not boot correctly on this hardware.

For a rough sense of the trade-off, Held Games (2026) reports about 150 MB of RAM overhead and a 15-second boot for KNULLI, versus about 60 MB and an 8-second boot for muOS. These are that source’s figures, not a guarantee for every build or device. Handheld Index (2026) describes muOS first boot as taking 60–90 seconds to reach the home screen; the KNULLI project cautions that its first boot can take quite long while it expands and formats the games partition. Treat first boot separately from later startup.

PortMaster and update behavior can vary by firmware version. KNULLI Scarab’s quick-start documentation says to install PortMaster from Ports after connecting to Wi-Fi; do not assume it is already installed. muOS support for PortMaster and over-the-air updates has been described inconsistently in older guides, so check the current muOS site and its release notes rather than relying on an old comparison table. If you want to try both muOS and KNULLI, flash each to its own TF1 card and leave the game card alone.

How do I back up the factory card?

Before flashing anything, copy the entire supplied card to a folder on your computer. This preserves a fallback copy of configuration, saves, BIOS folders, and any art or other files you may need. If the card contains games that a reseller preloaded, copying them is not proof that you have permission to use or redistribute them.

1. Turn the handheld off fully.
2. Remove the microSD card and insert it into the computer using a reader.
3. Copy all visible folders and files to a clearly named backup folder. If the computer does not show every partition, use the firmware project’s instructions for preserving any needed data.
4. Open the backup and confirm that important save and BIOS folders are present before setting the original card aside.

If you are migrating from an older custom setup, also back up saves, BIOS files, scraped artwork, and RetroArch overrides. Do not rely on the supplied card as your only copy of a save.

How do I install firmware on an ANBERNIC RG35XX, RG40XX, or RG35XX SP?

Download the matching image, flash it to a new TF1 card, and boot with the other card slot empty for the first setup. The exact device image matters more than the particular flashing program; flashing erases the selected card.

1. Choose the firmware and exact model. For stock, start at ANBERNIC’s download page. For muOS, use its device page. For KNULLI, choose the exact model image from the official GitHub releases. A KNULLI example filename is knulli-h700-rg35xx-plus-scarab-20260511.img.gz; that file is for the RG35XX Plus, not every RG35XX.
2. Check the release notes and checksum. Verify SHA-256 if the project publishes a hash. The release page or project documentation is the authority for the correct image and any special steps.
3. Write the image to the new card. Rufus, Raspberry Pi Imager, and Win32 Disk Imager are Windows options; balenaEtcher and Raspberry Pi Imager work on macOS and Linux. KNULLI also documents dd for users who already know how to use it safely. Rufus users should select image/DD mode when prompted. Rufus typically takes 3–5 minutes according to Held Games (2026), but time varies with card, reader, and computer.
4. Select the physical microSD card carefully. Confirm its capacity and drive identity in the flashing app before starting. Do not select a computer’s internal drive. The write operation erases the selected card.
5. Leave the flashed card alone afterward. Do not reformat partitions just because a computer reports that some are unreadable. KNULLI says not to manually format the card after writing; it handles the needed setup itself. If the writer accepts the compressed KNULLI .img.gz file, you do not need to extract it first.
6. Insert it into TF1/SYS and boot. For KNULLI’s first boot, put the OS card in the device and remove cards from the other slot. Let it finish expanding and formatting its games partition before interrupting it. Then follow the firmware’s prompts for initial configuration.

If a screen stays black, the sound is missing, or buttons do not respond, suspect a wrong image before assuming the handheld is broken. Recheck the rear-shell model name and release device list, download the image again, and reflash a known-good card. A poor or fake card can also cause boot failures.

How should I format TF2 and organize game files?

Use the format and folder structure required by the firmware you chose. exFAT is convenient when you will move files directly using Windows or macOS; EXT4 can suit KNULLI ports and saves but is not natively writable on those desktop systems. FAT32 remains part of MinUI’s documented setup, but it has a 4 GB per-file limit that rules it out for some large disc images.

Firmware	Second-card setup	Trade-off
Stock	Create ROM and BIOS folders, then the system subfolders expected by the firmware.	Follow the stock image’s own folder names; do not assume every build uses the same tree.
muOS	Format the games card as exFAT as directed by the current setup guide, then follow the muOS add-content instructions.	Commonly cited ROM roots include /mnt/mmc/ROMS or /ROMS/ on the second card; BIOS locations vary by version.
KNULLI	After first boot, insert TF2 and use Start → Storage → Format Second SD Card. Choose EXT4 or exFAT.	EXT4 is useful for some PortMaster ports and games-card saves, but computer-side access generally requires network transfer or extra tools. exFAT is easier to write from Windows and macOS; KNULLI may keep saves on Card 1.
MinUI	Use FAT32 on TF2 and follow the package instructions for ROMS, BIOS, and SAVES.	FAT32 cannot store an individual file larger than 4 GB.

For KNULLI, Batocera-style system folder names include gba, snes, psx, n64, gbc, genesis, and ports. Use the current firmware documentation to confirm names and any BIOS subfolders. Do not assume a folder named games works across all systems.

How can I add games without removing the SD card?

Use a network transfer feature only if your device has Wi-Fi and your firmware supports it. Otherwise, power down and copy files to TF2 with a card reader. The RG35XX 2024 and RG28XX are identified by ROMKADE and Stock OS MOD documentation as models without Wi-Fi, so a wireless transfer workflow will not work on those devices.

Option 1: Copy with a card reader

1. Shut the handheld down completely before removing the game card.
2. Insert TF2 into the computer and copy your files into the correct system folder.
3. Eject the card safely, reinsert it, and start the handheld.
4. Refresh or update the game list if the firmware does not find new files automatically. In KNULLI, use Start → Game Settings → Update Game Lists.

Do not pull the card during a write or while the handheld is saving. That can corrupt files or saves, and repeated removal puts wear on the card slot.

Option 2: Transfer over Wi-Fi

Some firmware exposes shared folders over the network. ROMKADE’s October 2026 folder reference lists these common roots: stock and Stock OS MOD at /mnt/mmc/Roms; KNULLI at /userdata/roms; muOS at /mnt/mmc/ROMS; ROCKNIX/JELOS at /storage/roms; and MinUI at /mnt/SDCARD/Roms. Exact access and folder visibility depend on firmware version and network setup.

For KNULLI, connect the handheld to Wi-Fi and note its IP address. On Windows, try \KNULLI or \[IP address] in File Explorer; on Mac, try smb://KNULLI in Finder’s network connection dialog. Held Games gives the KNULLI Samba default as username root and password linux. If you change credentials or the firmware changes its defaults, use its current network documentation rather than assuming these values apply to other systems.

KNULLI’s quick-start advice for connection trouble is to avoid WPA2+WPA3 mixed encryption and use WPA1+WPA2 instead. Community troubleshooting also points to 2.4 GHz as a useful option when a mixed 2.4/5 GHz network is unreliable. These are compatibility workarounds, not a reason to weaken a network permanently; use the least disruptive change your router permits and restore your preferred settings afterward.

Stock OS MOD has a self-hosted Game Manager web interface for managing games without removing the card. ROMKADE Manager is another PC-side option documented for Wi-Fi transfer; it runs as a Docker application and requires SSH and the handheld and computer to share a network. It does not solve the no-Wi-Fi limitation on the RG35XX 2024 or RG28XX.

Which games and BIOS files can I add legally?

Use games you have dumped from cartridges or discs you own, homebrew and freeware that are licensed for free distribution, or compatible ports that require data files from a game you purchased. Laws differ by country, and owning a cartridge does not automatically make downloading a ROM from a third party lawful.

• Your own dumps: make copies from your own physical media using your own equipment, and follow the law where you live.
• Homebrew and freeware: check the individual title’s license and redistribution terms before copying or sharing it.
• PortMaster ports: some are free engines that need game data from a copy you bought. Examples include OpenMW using Morrowind data, along with Stardew Valley, DevilutionX, Fallout CE, and Doom-related ports. The port’s availability does not provide the commercial game data.
• BIOS: the cautious approach is to dump BIOS from hardware you own, rather than download a public BIOS pack. BIOS copyright is a separate issue from ownership of the console.

Tech Insider’s October 2026 article says downloading copyrighted ROMs you do not own is illegal in most jurisdictions, even if you own the original cartridge or disc. No primary copyright-office circular or court judgment establishing a universal personal-backup rule is identified here, so do not treat a forum post or general online consensus as a legal guarantee. Check the applicable law in your jurisdiction. ANBERNIC’s pulled stock firmware 1.0.6 reportedly included an app for downloading ROMs over Wi-Fi; the availability of an in-device download feature would not itself establish that a game is legally distributable.

For KNULLI, the missing-BIOS check is under Main Menu → Game Settings → Missing Bios Check. Scraping artwork or metadata is optional and does not make a game file legal to possess.

What should I configure after the first boot?

Set the basics first, then add optional network and presentation features. A clean setup is easier to troubleshoot than changing many settings at once.

1. Confirm the model and clock. muOS asks you to confirm the device type and set the clock during first setup. Check that the displayed model is correct.
2. Set up TF2 and add a small test batch. Confirm that the firmware sees the second card and that files appear in the expected systems before copying a full library.
3. Connect Wi-Fi if available. This enables network transfer, scraping, and network-dependent features. On KNULLI, RetroAchievements require a live network connection.
4. Add optional accounts or metadata. KNULLI can use ScreenScraper, TheGamesDB, and ArcadeDB for scraping. A ScreenScraper account is optional; scraping only adds presentation data.
5. Install ports deliberately. On KNULLI Scarab, connect to Wi-Fi and use Ports → Install.PortMaster to install PortMaster. Ports may require separate game files that you must supply lawfully.
6. Back up saves before experimenting. muOS includes Backup Manager, which Retro Game Corps recommends using before a reflash. Keep a separate copy of important saves on your computer.

KNULLI users can adjust themes under Updates & Downloads → Themes; Art-Book-Next-ES is one option recommended by community documentation. Other optional settings include disabling frontend music, choosing an overclock setting under System Settings → Overclock, and changing confirm/cancel behavior in Frontend Developer Options. Avoid changing performance settings before you know that the device is stable at its defaults.

Will custom firmware make more demanding games run better?

Not by itself. The H700 family uses an Allwinner H700 with 1 GB LPDDR4 RAM, and changing from stock to muOS or KNULLI does not replace that hardware. A different interface may change the feel of navigating or launching games, but it cannot turn the handheld into a newer console.

Handheld Index describes pre-PS1 systems and arcade games as the H700’s comfortable range, with lighter N64 and Dreamcast titles as selective possibilities. It says PSP is not realistic on RG35XX-class H700 models, and PS2, GameCube, and Wii are outside the target. Other coverage is more optimistic about PS1, PSP, and many Dreamcast games on the RG40XX H/V; that reflects a different device-specific performance claim, not a promise that every title runs smoothly. A game that starts is not necessarily a game that runs at full speed.

For practical expectations, judge performance by the particular device and game rather than the firmware label. If your main goal is demanding later-generation emulation, choose hardware designed for that workload instead of expecting a new SD card or launcher to remove the H700’s ceiling.

Can I undo a firmware installation, and does it affect the warranty?

On the dual-slot Linux XX devices covered here, installing custom firmware is a software change made by swapping the microSD card; you do not need to open the handheld. Keep the original card and use a new card for custom firmware. Removing that card lets you return to the device’s stock setup, subject to the way that particular model boots.

Community guides describe the change as reversible and say a software-only card swap does not affect the hardware warranty. That is not a legal warranty opinion or a guarantee about every seller’s terms. Check the warranty terms that came with your unit, avoid opening or modifying the hardware, and preserve the factory card before making changes.

Frequently Asked Questions

Can I use the same games card with both muOS and KNULLI?

Often, but do not assume every system folder, save path, or metadata file is portable between them. Keep a backup of saves and check each firmware’s current add-content instructions before switching the card.

Why does my computer say the flashed microSD needs to be formatted?

A bootable firmware card can contain partitions your computer does not recognize, so a format prompt after flashing is not proof that the image failed. Cancel the prompt and do not reformat the card; boot it in the handheld and follow the firmware’s first-run instructions.

Can I use a 1 TB microSD card in an ANBERNIC XX handheld?

The cited guidance supports 64 GB or larger game cards and gives 128 GB as a practical example, but it does not confirm a universal maximum capacity for every model or firmware. Check the exact model and firmware documentation before buying a much larger card, and verify the card’s real capacity before loading files.

Does a preloaded game card make its ROMs legal to use?

No. A card seller’s decision to include files does not establish that the seller had rights to distribute them or that you have permission to use them. Apply the same ownership, license, and local-law checks you would use for files copied from any other source.