MrCART128 brings 16 MB storage and MP3 audio to Nintendo Virtual Boy

Nintendo’s Virtual Boy is getting a new multicart, and this one brings more than extra storage. The MrCART128 packs 16 MB of flash memory, faster game loading and a dedicated audio system capable of playing MP3 music and WAV sound effects. Developed from the original MrCART by Mr. Flower, the new cartridge is available to pre-order through RetroOnyx for $235, with the first shipments expected in November 2026.

Four times the storage of the original MrCART

The original MrCART came with 32 Mbit of flash memory. Its successor increases capacity to 128 Mbit, giving users 16 MB of storage for individual Virtual Boy games and applications. It’s a considerable increase, particularly for larger software projects. The MrCART128 can accommodate games exceeding the original cartridge’s storage limit, opening up more room for developers working on larger Virtual Boy releases.

Loading speeds have received attention, too. The new hardware can flash games up to three times faster than its predecessor, cutting the time needed to transfer software from a microSD card into the cartridge’s internal memory.

Users can store their game collections on microSD cards with capacities up to 32 GB. The cartridge supports folders and subfolders within its GAMES directory, making it possible to organise software and select individual titles through the Virtual Boy’s on-screen menu.

There’s no need to connect the cartridge to a computer whenever you want to change games. Select a title, flash it to the cartridge and start playing. Firmware updates work through the microSD interface, removing the need for a separate programming device during normal operation. An ARM-based system-on-chip manages the cartridge’s internal functions, with 16K × 8 nvSRAM providing storage for game save data.

ESSound brings MP3 music and WAV effects to Virtual Boy

Storage isn’t the only major change. The MrCART128 introduces ESSound, a dedicated audio expansion system built around the Virtual Boy’s ES expansion address space. The system supports stereo MP3 music and WAV sound effects stored directly on the microSD card. Both formats can play simultaneously, giving developers access to prerecorded music, sampled speech and digital effects.

The console’s original VSU sound hardware remains available, so games can combine their existing audio functions with the new digital playback system. It’s a different approach from relying entirely on the Virtual Boy’s built-in sound capabilities.

Developers can control audio playback through software commands covering starting and stopping tracks, looping, volume adjustments and stereo balance. Games access audio files from their respective directories on the microSD card.

There’s one distinction worth making. ESSound won’t automatically improve the audio in existing Virtual Boy games. Software must support the new interface before it can use MP3 playback or the expanded sound effects. For developers creating compatible games, the system provides more options for handling music, dialogue and effects without replacing the console’s original sound hardware.

A familiar cartridge with new hardware inside

The MrCART128 retains the dimensions of a standard Nintendo Virtual Boy game cartridge. It fits into the console’s existing cartridge slot and doesn’t require modifications to the system. RetroOnyx uses an anodised aluminium housing for the cartridge, with newly manufactured internal components rather than electronic parts recovered from original Virtual Boy games.

The package includes the cartridge itself, a dust cover and a protective sleeve. You’ll need to supply your own microSD card and software. Despite the increased storage and new audio capabilities, the basic process remains familiar to anyone who has used the original MrCART. Games live on the microSD card, and users select their preferred title through the console before loading it into flash memory. The cartridge combines its new hardware with a straightforward method of managing multiple games on a single device.

MrCART128 price and release date

RetroOnyx has opened pre-orders for the MrCART128 at $235, with production planned around the initial order volume. Circuit board orders are expected to follow approximately three to four weeks after pre-orders begin. Fabrication and assembly will take place before the first cartridges ship, currently scheduled for early November 2026. The delivery window remains an estimate and could change depending on manufacturing and assembly schedules.

For Virtual Boy owners, the MrCART128 brings several hardware improvements together in one cartridge. Its 16 MB flash capacity supports larger games, faster flashing reduces loading times, and microSD storage provides a convenient way to manage multiple titles. ESSound introduces another set of possibilities for developers, adding stereo digital audio to the console’s existing sound system without requiring changes to the Virtual Boy itself.

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