An RP2040-based PC-FX Development Cartridge

November 2, 2024 by Dave Rowntree 3 Comments

[David Shadoff] has a clear soft spot for the NEC console systems and has been collecting many tools and data about them. When developing with these old systems, having a way to upload code quickly is a real bonus, hence the creation of the PC-FX Dev Cart. Based on the Raspberry Pi RP2040, the custom cartridge PCB has everything needed to run software uploadable via a USB-C connection.

While the PC-FX is a CDROM-based system, it does sport a so-called FX-BMP or backup memory port cartridge slot, which games can use to save state and perform other special functions. Under certain circumstances, the PC-FX can be instructed to boot from this memory space, and this cartridge project is intended to enable this. Having a quick way to upload and execute code is very useful when exploring how these old systems work, developing new applications, or improving the accuracy of system emulators. The original FX-BMP cartridge has little more inside than a supercapacitor-backed SRAM and a custom interfacing IC, and of course, it would be quite a hassle to use this to develop custom code.

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Building A DIY MSX Mega Cartridge

September 7, 2024 by Dave Rowntree 9 Comments

[Mike] from Leaded Solder has a soft spot for old computers, and a chance encounter with a friend sent them deep down the deep hole that is the world of 80s and 90s-era Japanese home computers. Many people playing with these machines have all kinds of issues to deal with, such as rotting cartridges, failing components, and just dirt and mank in critical places. [Mike] decided that working on an MSX-standard custom programmable cartridge would be sensible, but then got stuck on how the MSX cartridge mapping works.

The Konami 128K scheme uses 4 to 4-of-8 mapping.

You may recall that the MSX platform is not a single computer but a standard to which many (mainly Japanese) manufacturers designed their products. This disconnected the software writers from the hardware makers and is essentially a mirror of the IBM-PC clone scene.

The MSX is based around the Z80, which has a 16-bit address bus, restricting it to 64K of ROM or RAM. The MSX has two cartridge slots, an ‘internal’ slot for the BIOS and RAM and a fourth for ‘misc’ use. Each of these is mapped internally into the physical address space. The cartridge slots have 64K of addressable space mapped into the Z80 physical space.

If this was not complicated enough, many MSX games and applications exceeded this restriction and added a layer of mapping inside the cartridge using bank switching. A register in the cartridge could change the upper bits of the address allowing ROMs larger than 64K.

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Left: the ATtinyBoy and cartridges inside a custom case. Right: ATTinyBoy under the hood.

2024 Tiny Games Contest: ATtinyBoy Does It With Tiny Cartridges

August 31, 2024 by Kristina Panos 3 Comments

What is it about tangible media? There’s just something neat about having an individual thing that represents each game, each album, each whatever. Sure, you can have a little console with a thousand games loaded on it, but what’s the fun in that?

Enter the ATtinyBoy. [Bram]’s entry into the Tiny Games Contest is based on the ATtiny85, and the whole thing is smaller than a credit card. In fact, each little game cartridge contains its own ATtiny85, with the pins broken out into headers.

That is, although the schematic is based on [Billy Cheung]’s gametiny, which uses an ATtiny85 as the brain, ATtinyBoy’s brain is divided among each of the games.

This certainly checks a lot of boxes when it comes to contest rules and requirements, and it’s just awesome besides. We particularly like the custom box that holds ATtinyBoy and all his distributed knowledge. If you want to make one of your own, the schematic, code, and STLs are all available over on IO.

A Look Inside The Super Nintendo Cartridges And Video System

July 31, 2024 by Maya Posch 22 Comments

Despite being effectively sold as a toy in the 1990s, the Super Nintendo Entertainment System (SNES) was pretty bleeding-edge as far its computing chops were concerned. This was especially apparent with its cartridges, such as in this excellent summary article by [Fabien Sanglard].

In addition to the mask ROM that stored the game data and (optionally) battery-backed SRAM to store save data, a wide range of enhancement processors existed that upgraded the base SNES system with additional processors for more CPU performance, enhanced graphics and so on. Imagine sticking a game cartridge in a PlayStation 4 today that boosted CPU speed by 5x and gave it a much better GPU, this was the world of SNES games.

On the other side of the video game cartridges was the video output system, which seems easy enough in today’s world of digital HDMI and DisplayPort output. In the 90s video output did however mean NTSC and SECAM/PAL, which means playing nice with frequencies, different resolutions (lines) and squeezing as much as possible into a single frame in a way that works with the game console’s rendering pipeline. As a result of this the PAL version of Super Mario World has a larger vertical resolution than the NTSC version (240 vs 224 lines), even if it’s still squashed into the same 4:3 format. For the physical video output side, European gamers were spoiled with an AV connector to (RGB) SCART output, while the rest of the world dealt with some variety of RF composite or S-video.

Although the SNES’s successor in the form of the N64 would not take cartridges to the same extremes, it was this flexible architecture that gave the SNES such an amazing game library.

Making SD Cards More Nostalgic With More Cartridge-ness

July 12, 2024 by Maya Posch 11 Comments

As practical SD cards are, they lack much of what made floppy disks and cartridges so awesome: room for art and a list of contents, as well as the ability to not be lost in shaggy carpet or down a pet’s gullet. In a fit of righteous nostalgia, [Abe] decided that he’d turn SD cards into cartridges in the best way possible, and amazingly managed to not only finish the project after two years, but also make it look snazzy enough to have come straight out of the 1980s. The resulting cartridges come both with fixed (256 MB) and removable micro SD card storage, which are mounted on a PCB that passively connects to pogo pins in the custom, 3D printed reader.

Front of an SD-card-turned-cartridge with adn without decal. (Credit: Abe's Projects, YouTube) — Front of an SD-card-turned-cartridge with and without decal. (Credit: Abe’s Projects, YouTube)

The inspiration for this project kicked in while [Abe] was working on a floppy drive conversion project called the Floppy8, which crammed an MCU into an external floppy drive along with a rough version of these SD card-based cartridges that used the physical card’s edge connector to connect with a micro SD slot inside the converted floppy drive. The problem with this setup was that alignment was terrible, and micro SD cards would break, along with a range of other quality of life issues.

Next, the SD card was put into a slot on the carrier PCB that featured its own edge connector. This improved matters, but the overly complicated (moving) read head in the reader turned out to be very unreliable, in addition to FDM printed parts having general tolerance and durability issues. Eventually a simplified design which takes these limitations in mind was created that so far seems to work just fine.

Although SD cards in cartridges are not a new idea, using them purely as a data carrier is far less common. One could argue about the practicality of turning a fingernail-sized micro SD card into something much larger, but in terms of aesthetics and handleability it definitely gets an A+.

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Fail Of The Week: [Mark] Makes An Atari Cartridge

December 7, 2023 by Al Williams 8 Comments

Part of the magic of the movies is that the actors always know what will happen next. There never has to be a scene where James Bond orders wine, and the sommelier has to correct his pronunciation, or he miscounts his hand at baccarat. Real life is rarely as smooth. Of course, YouTube is more akin to a movie than real life, and we always wonder how many flawlessly executed projects you see on YouTube really went that well. [Mark Fixes Stuff] left no scenes on the cutting room floor, though, in his realistic portrayal of his quest to build a nice-looking Atairi 2600 cartridge. Watch it below.

Spoiler alert: In the end, it all worked out. But getting there was a series of misadventures. Starting out with [Parker Dillman’s] PCB, he put together the insides of the cartridge, including a socket for the EPROM. He then resin-printed a case. Like many of our own projects, the first run wasn’t quite the size he expected. It was probably close enough, though, but then he realized the socket made the board too tall to fit in the enclosure.

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Super NES Cartridge Pulls A Sneaky, Plays Minecraft

August 31, 2023 by Donald Papp 24 Comments

Sometimes it’s the little touches and details that make a project. That’s certainly the case with [Franklinstein]’s Super Nintendo (SNES) Cartridge Hard Drive. It might only be an enclosure for a solid-state hard drive with a USB interface, but the attention to detail is what really makes it worth checking out.

A SNES cartridge has a pretty standard clamshell-ish construction, but fitting the solid-state drive plus cable adapter turned out to be a bit of a challenge.

Since [Franklinstein] wanted the cartridge to look as original as possible, careful measuring and cutting was needed to securely fit the drive and provide an unobtrusive USB-C port tucked discreetly into the cartridge’s opening. We like the technique of using a 3D printed fixture to take up the slack on the cable by exactly the right amount, resulting in a 100% rattle-free end product. A custom Minecraft sticker label provides the finishing touch.

Being able to plug it into a computer and actually play Minecraft is a neat gimmick, but it really shows that some careful construction and assembly can be what makes something look like a clean build instead of a hack job. Take a look at additional build detail and pictures, and check out the video of the build, embedded below.

Hey, if sneaky cartridge mod tricks intrigue you, then you’ll absolutely want to check out how it was possible to play DOOM on a NES from a cartridge. Maybe that’s the next evolution for a cartridge with a Minecraft label on it?

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