Introduction
Over the nearly twenty years since the original FlashBoy Cart was released, there has been tremendous progress in the Nintendo Virtual Boy flash-cart scene. We’ve seen improvements ranging from all-new hardware components and larger amounts of flash memory to SRAM save support and the ability to run increasingly ambitious homebrew games such as Hyper Fighting. However, one major feature has remained absent from most Virtual Boy flash carts: the ability to flash games without the need for a PC.
For Mac users like myself, this has been particularly frustrating, as many of the existing solutions have relied on Windows-based software. That is where Mr. Cart comes in. Mr. Cart is the first Virtual Boy flash cart to offer an on-screen menu that allows you to select a game from a MicroSD card and flash it directly from the Virtual Boy itself. After spending some time putting it through its paces, I think it is a pretty impressive addition to the Virtual Boy homebrew scene.
The Story Behind Mr. Cart
Mr. Cart was created by Mr. Flower, a well-known member of the Virtual Boy community and contributor to the famed Planet Virtual Boy community. The original Mr. Cart was released in May 2025, however with the Virtual Boy is such a niche system, manufacturing and distributing a product like independently was challenging to say the least. To help expand its availability, RetroOnyx, a site operated by renowned Virtual Boy homebrew guru Kevin Mellott, received permission to produce and distribute Mr. Cart to a wider audience. This partnership provides several advantages. Unlike older solutions that may require dismantling original cartridges for donor parts, Mr. Cart now produces these using all-new components. RetroOnyx also produces the cartridge in a high-quality anodized aluminum shell. For Virtual Boy enthusiasts, that is a pretty significant upgrade with the RetroOnyx-style flair.
Hardware
Inside Mr. Cart is 32MBit of flash memory, along with SRAM for save support. The cartridge features an anodized aluminum shell and a MicroSD card slot for storing Virtual Boy ROMs which supports MicroSD cards up to 32GB. However, I would recommend using a 4GB or 8GB card instead. Even 4GB is considerably more storage than the Virtual Boy really needs, and there are some limitations to the number of files Mr. Cart can display. Those limitations aren’t major, but they are worth knowing about.
Setup and User Interface
One of Mr. Cart’s biggest advantages is its simplicity. The file structure is straightforward, and the necessary files can be downloaded from Stone Age Gamer. Their website also provides a link to the original Mr. Cart website, which contains additional information about the cartridge. Once your MicroSD card is prepared, simply insert Mr. Cart into the Virtual Boy and power the system on.
The first thing you’ll see is the Mr. Cart Main Menu, where your compatible ROMs are displayed. From there, select a game and let Mr. Cart flash it directly to the cartridge. No PC, no computer-based flashing software, just select the game and play.
Flash Times
Flash times depend on the size of the ROM.
| ROM Size | Approximate Flash Time |
| 512KB | ~8 seconds |
| 2MB | ~36 seconds |
| 4MB | ~54 seconds |
Since all official Virtual Boy releases fall between 512KB and 2MB, retail games should take no more than approximately 36 seconds to flash. That makes Mr. Cart considerably more convenient than older flash-cart solutions such as FlashBoy and HyperBoy, particularly when comparing the experience to flashing games through a PC.
100-File Limit Limitation and sub folder support
The first limitation is the number of files that can be displayed. Mr. Cart currently shows only the first 100 games or programs on the MicroSD card. You can store more than 100 files on the card, but anything beyond the first 100 will not appear in the menu.
Mr. Cart also does not currently support multiple folders. This means you cannot organize a large library into separate directories for games, demos, utilities, homebrew, and so on. For a smaller library, this isn’t a major issue. However, it becomes more noticeable if you are trying to keep a large collection organized.
4MB+ Software Limitations
Another limitation involves larger homebrew projects. As of the time of this writing, demos or programs larger than 4MB will not flash properly and/or may crash when attempting to run.
The most notable examples I am aware of are:
- Bad Apple — 16MB
- Hyper Fighting Raw Version — 16MB
For most Virtual Boy software, this isn’t going to be an issue, but it is something to keep in mind if you’re primarily interested in larger homebrew projects.
Filename Restrictions
There is also a relatively minor filename restriction. Some homebrew demos and programs use particularly long filenames. Files appear to need to be limited to approximately 34 characters or fewer in order to appear in the Mr. Cart menu and also need to be in .vb file format. I encountered this myself with several homebrew programs and had to rename them before they appeared. It’s definitely a minor annoyance rather than a major problem, but it’s worth mentioning.
Real-World Testing
I have put Mr. Cart through a battery of tests, and overall, I am very impressed with the experience. One of my favorite features is the game-selection menu. The interface has a familiar feel similar to the menus found on many EverDrive cartridges from Krikzz. It is simple, straightforward, and very easy to navigate. Once a game is loaded, I haven’t encountered any problems with either gameplay or sound.
Everything runs smoothly, and the experience feels essentially identical to playing the original retail cartridge.
Build Quality
The RetroOnyx-branded Mr. Cart is housed in an anodized aluminum shell, and it looks fantastic.
The metal construction gives the cartridge a premium appearance while also providing a nice, even weight balance. It feels like a substantial piece of hardware rather than simply an inexpensive reproduction cartridge. The red and black color options also give buyers some choice in how they want their cartridge to look.
Price
Stone Age Gamer currently sells Mr. Cart for $249.99 and although this is a significant amount of money for a flash cartridge, most FlashCarts for the Virtual Boy are at this price point or even higher. The other carts do not have the on-screen menu or even have a MicroSD or equivalent storage option. Mr. Cart offers something that previous solutions haven’t, a completely PC-free way to select and flash games directly from the console. For serious Virtual Boy enthusiasts, that convenience is a major selling point. For anyone that is interested in purchasing this cart from the wonderful team at Stone Age Gamer, please go to the link provided to purchase the product directly from them.
Mr. Cart offers something that previous solutions haven’t, a completely PC-free way to select and flash games directly from the console.
Final Verdict
Mr. Cart is an excellent addition to the Virtual Boy flash-cart scene. Its biggest accomplishment is also its simplest: you can put your ROMs on a MicroSD card, insert the cartridge into your Virtual Boy, select a game from the on-screen menu, and flash it without ever touching a PC, once setting up the file structure on the MicroSD card. The 100-file limit, lack of folder support, filename restrictions, and inability to properly handle certain software larger than 4MB keep it from being perfect, however for the vast majority of Virtual Boy software, these limitations are relatively minor.
The combination of easy on-console game selection, PC-free operation, MicroSD storage, and excellent build quality makes Mr. Cart one of the most convenient Virtual Boy flash-cart solutions available. If you’re a serious Virtual Boy collector, homebrew enthusiast, or simply someone who wants an easier way to play a large library of Virtual Boy software, Mr. Cart is an impressive piece of hardware and a welcome evolution of the Virtual Boy flash-cart scene.
Specifications
Platform: Nintendo Virtual Boy
Type: Multi-Flash Cartridge
Flash Memory: 32MBit
Save Support: SRAM
Storage: MicroSD, up to 32GB
Tested MicroSD Size: 8GB
Price: $249.99
Available From: Stone Age Gamer
