Many people have asked us whether it’s possible to hand-assemble a Raspberry Pi. While the use of fine-pitch BGAs and PoP memory make this impossible, I thought you might like to see how one of my home-made prototypes of a $25 computer looked back in 2006, before I gave up on DIP chips, through-hole components and veroboard.
These boards use an Atmel ATmega644 microcontroller clocked at 22.1MHz, and a 512K SRAM for data and framebuffer storage. 19 of the Atmel’s 32 GPIO lines are used to drive the SRAM address bus. To generate a 320×240 component video signal, the Atmel rapidly increments the address, and the data lines are fed via 74HC-series buffers to a trio of simple summing-point DACs; during horizontal and vertical blanking, it is free to perform other operations. Here’s a video of the device in action.
Way back in 2006, we considered building a $25 educational computer around an Atmel microcontroller. Here’s a video of a prototype generating component video and doing some simple 3d graphics.
Not quite Quake 3, I’m sure you’ll agree, but maybe familiar to fans of David’s 1987 classic Zarch. In the end, I felt that much higher performance, and the ability to run a general-purpose operating system, outweighed the benefits of home assembly, but it’s still a neat design. Those of you interested in the gory details can download Easy-PC schematics
and a PCB layout here.