Dual-Port Memory And Raspberry Pi Team Up For Retro Console Multicart

There’s something powerful about reliving the experience of using a game console from our personal good old days, especially the tactile memories stored up from hundreds of hours handling a chintzy joystick or the sound and feel of inserting a game cartridge. Emulators have their place, but they fall far short of period-correct hardware in the nostalgia department.

That’s not to say that the retro gear can’t use a little help in terms of usability, which is why [Scott M. Baker] built this Raspberry Pi multi-cartridge for his Atari 5200. The idea is to maintain the experience of the cartridge interface without having to keep stacks of cartridges around for all the games he wants to play. [Scott] leveraged the approach he used when he built a virtual floppy drive for a homebrew PC/XT: dual-port memory. The IDT7007 is a 32k chip that lives between the Atari 5200 and a Raspberry Pi Zero and can be addressed by both systems; the Pi to write ROM images to the memory, and the console to read them. He had to deal with some fussy details like chip select logic and dealing with the cartridge interlock signals, not to mention the difference in voltage between the memory chip’s logic levels and that of the Pi. Retro game-play occupies the first part of the video below; skip to 6:45 for build details.

The one quibble we have is trying to jam everything into an old cartridge. It’s critical to replicating the tactile experience, and while we don’t think we’d have gone so far as to injection mold a custom cartridge to house everything without any protrusions, we might have 3D-printed a custom cartridge instead. In the end it doesn’t detract much from the finished project, though, and we appreciate the mix of old and new tech.

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Making Vintage Computing Easy, The Hard Way

If you want to not take for granted how easy and seamless computers have become, take up vintage computing as a hobby. If you venture down the retro path, you’ll quickly question how anyone ever got any useful work done with computers, and the farther back you go in computer history, the more difficult everything seems to become.

Case in point: how do you easily transfer files between a home-brew PC/XT and your modern desktop? Back in the day we did it with null modem cables or by sneaker-netting stacks of floppies, but [Scott M. Baker] found another way — putting a Raspberry Pi on the ISA bus as a virtual floppy drive. The heart of the ISA card is an IDT7130, a 1-kb RAM chip that allows simultaneous asynchronous access over dual ports. One port talks to the ISA bus and the other talks to the GPIO of the Pi, after level-shifting to make everything voltage compatible, of course. [Scott] wrote a driver for the card, plugged a Pi Zero W into the header pins, and threw a Python server together that makes local images available to the shared memory on the card. The upshot of this is that the retro machine thinks it has a floppy in it, but it’s actually a server. The video below has tons of detail and shows the card in action. Pretty slick.

[Scott]’s projects are always fun to check out, and he really seems to have the retro life dialed in. Whether it’s old jukebox hacks or a Unix-ish OS for Z80s, there’s plenty to learn. Although we’d like to see more about that PC/XT in the video; are those Nixies we spy along the front panel?

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Dual Porting a C64 Flash Cart

The old cartridges for the Commodore 64 use EEPROMs to store their data, and the newer Flash carts use either a Flash chip or an SD card to put a whole bunch of games in a small plastic brick. [Stian] and [Runar] thought that wasn’t good enough – they wanted to program cartridges in real time, the ability to reboot the C64 without ever touching it, and a device for coding and testing. What they came up with is the latest advance in Commodore cartridge technology.

The device presents 8k of memory to the C64, but it doesn’t do this with Flash or an EEPROM. Instead, [Stian] and [Runar] are using a dual-port static RAM, specifically one from the IDT7005 series. This chip has two data busses, two address busses, and /CE, /OE, and R/W lines for either side of the chip, allowing other digital circuits to be connected to one small section of the C64’s memory.

Also in the cart is an ATmega16 running V-USB to handle the PC communications. It takes about 1 to 1.5 seconds to transfer an entire 8k over to the cartridge, but this chip can read and write the RAM along with the C64 simultaneously.

If you want a box that will give you the ability to put ever game in existence on a single cartridge, this isn’t the one. However, if you want to write some C64 games and do some live debugging, this is the one for you. The Eagle files are available, and there’s a video demo below.

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