Running DOOM on weird obscure hardware is a fun hacker pastime that’s been around for a long time now. It’s always enjoyable to see someone port it to an egg timer, or a hat, or whatever else. But what about running the iconic shooter on a CPU of your very own? [Armaan] and [Liam] have done just that.

The CPU in question was designed at the logic gate level, deployed on to an FPGA, and hooked up with the necessary peripherals to run as a going concern. Early testing of the CPU involved running straightforward code to generate Mandelbrot sets and to play a simple game of Pong. But [Armaan] and [Liam] had bigger goals: to port the game that everybody ports to everything. Doing that took some work.

To get DOOM running, the CPU had to get faster, and it needed many tweaks to how memory was handled. There was also work to be done to create a keyboard interface, an HDMI video output, and a hardware timer. From there, the game itself had to then be ported to the custom CPU’s architecture. Eventually, the duo had the game running… at a glacial 0.7 FPS. A success, but not the magical end result that was desired. A bump to clock speed and further optimizations and compiler tweaks eventually got the game up to an impressive 15-20 FPS. The goal for future work is to push it to an entirely-playable figure of 30 FPS or better.

It’s worth checking out the (apparently unembeddable) videos on Instagram to see the CPU in action. We’ve also featured plenty of fun DOOM ports before, too. If you’re brewing up custom CPUs or DOOM ports of your own, keep them coming to the tipsline. The latter in particular is often a wonderful milk run for the writer that happens across it. Happy hacking out there!

Perhaps the most ridiculous statement that anyone can make is that a computer system with clearly enough processing power ‘cannot run DOOM‘. This is why we accept the premise that a PDP-11 cannot run this game, but something on the order of a Neo Geo gaming console with its 68000 processor and for the time impressive GPU definitely ought to be able to.

The stated problem here is a lack of RAM for a framebuffer, with the CPU only having 64 kB to play with. This limitation now has seen two different approaches to try and circumvent it, as covered by [Modern Vintage Gamer].

The first project here is Doom64kB, which as the name suggests tries to somehow work with this system RAM limitation. It uses the Doom8088 port for the original IBM PC and similar Intel 8088-based systems. This had to massively reduce the feature list, including the lack of texture mapping for floors and ceiling, no saving or loading, and no music.

The other project is DoomGeo, which doesn’t try to bend the Neo Geo hardware to its will, but accepts the Neo Geo way of doing things: involving sprite strips, pre-baked graphics, fix-layer UI, and a minimum of runtime data. This of course drastically changes how the Doom game engine normally works, with its framebuffer-based rendering.

From this we can thus conclude that it’s not so much the processing power that limits where DOOM can run, but more of how framebuffer-friendly the system architecture is, yet with some ingenuity and a complete rewrite of the game engine even that is no major obstacle.

(Top image: Neo Geo AES console. Credit: Evan-Amos, Wikimedia)

Targeted towards refined female gamers unlike the savagery of the mainstream game consoles of the era, 1995’s Casio Loopy was a bit of an oddity of a game console. Despite being standard enough in its design and backed by the might of Casio, it saw only one year of active software development and hardware manufacturing ceased by the end of 1998. With only eleven titles released for the system, with none of them being Doom, this obviously terribly upset [Throaty Mumbo], who set out to right this egregious wrong.

For the two dozen people or so who have one of these systems, you can experience the fruits of his labor yourself via the GitHub repository and something like the FloopyDrive cartridge.. Despite the quite capable Hitachi SH-1 16 MHz CPU and 1 MB of RAM, the main limitation is probably the original 2 MB of ROM space that does not leave a lot of space for DOOM WADs, even after doubling it on the FloopyDrive. Correspondingly you only get a handful of levels out of it.

Overall game performance isn’t too bad, though in the port’s current unoptimized state the resolution is fairly low. That said, even the console’s built-in printer is supported and demonstrated in the video, which is a pretty nice touch. It’s not like Sega or Nintendo consoles allowed you to screenshot those glorious headshots.