Raspberry Pi – 2006 edition

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.

Veroboard and PCB versions of the prototype

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.

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.

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