Apple has released a few cards (The Houdini I, Houdini II, and DOS Compatibility Card) that had entire computers on them minus the hard drive, and were originally intended to only run DOS applications, including Windows 3.x and 95, that had an x86 CPU, a sound card on the Houdini II and higher, no FPU, none of the cards had any storage, and a VGA port, and I think some models have some other serial port I'm not too sure of. Certain Mac models came preinstalled with the DOS Compatibility Card. When it comes to using this in Linux, the cards come with lots of RAM (for it's time), with the most powerful card supporting up to 80 megabytes of RAM. About the CPU, I'm not too familiar with how the kernel supports CPUs internally, if the kernel can support different architectures on different cores, or have another CPU with a different architecture, but it could be supported if the kernel can handle this without making the computer slow, like reserving the x86 CPU for KVM exclusively. The VGA port on the unit can act as another port for a display, which can display the Linux GUI or terminal.
Information about this card can be found online quite easily, although some links require the Wayback Machine as they are decades old. WIP emulation for the Houdini II with a GPL v3 licence can be found: https://github.com/dingusdev/dingusppc/commit/90f22d806677048813e0c89216a6430076b5b00f with contact information for the reverse engineers that completed it. If you own this card or a Mac preinstalled with the card, you can try implementing this, and get extra RAM in return.
