For PropBerry, I was thinking using a Parallax Propeller* (or just Prop) as a super i/o co-processor for the RPi where the Prop would be used to offload the real-time I/O and let the RPi handle the higher program features. After talking about this combo on the Parallax forums, the Props VGA video capabilities were mentioned which got me thinking about using the PropBerry as a VGA serial terminal console and shelve the i/o co-processor idea for now.

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Uses the smallest and cheapest 32 bit CPU to generate 3D graphics and sound.
The RBox is a game console that is simple enough to build on the prototype area of an NXP LPC111X dev kit; no pcb required just a crystal, a few capacitors and resistors.

Features:

320x240 composite or s-video output generated entirely in software

256 colors with standard palette, up to 8k colors

8 bit 15khz stereo audio

~$1 Analog joystick

~$1 CPU

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Bit banger is my most constrained and minimalistic microcontroller-based demo yet. It won the Oldschool 4k compo at Revision 2011.
Bit banger is built around an ATtiny15 microcontroller, which runs at 1.6 MHz and has 1 kB of flash ROM and a claustrophobic 32 bytes of RAM. / the entire demo is cycle counted.

At a clock rate of 1.6 MHz, the visible part of each line of the VGA signal swooshes by in exactly 36 clock cycles. The entire line, including horizontal blanking, is 51 clock cycles wide. During this time, both graphics and sound must be generated.

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