In the early 80’s we lived in Silicon Valley, and it was in one of the ubiquitous Garage Sales there that I found a cardboard box full of blue printed circuit boards. Ever the pack rat, I bought it immediately and brought it to my own garage, where I found it to contain what must have been a homebuilt computer based on a Motorola 6800 8-bit CPU chip. The box contained a processor board, a backplane, and three boards like the one shown here, clearly parts of the system’s main memory.
The gold-lidded chips on the front are apparently 2147 4K static RAM chips. That’s 4K bit, not Byte; 500 Bytes per chip, or 24 K Byte for the entire board. Nothing unexpected here, this was hot stuff for mid-70’s technology. The surprise comes when you turn the board over: the chips are all interconnected by the technology called Wire Wrap, with hundreds of wires connecting the socket pins on the back side. Someone had painstakingly wired these memory boards by hand, pin by pin and wire by wire!
Yep… those were the days, when passionate hobbyists were at the forefront of the home computer revolution. I’m ashamed to recall that I, despite being a radio amateur and electronics hobbyist, did not join this action. I was already into full-fledged mini-computers at my workplace, and I remember thinking “these micro-computers won’t be of any use unless coupled with a Teletype (i.e., a keyboard and a printer), and no private citizen will ever be able to afford one of those”. It was only when the Commodore 64 arrived on the scene that I started into home computing in earnest.
Exhibit provenance: As I said, a Garage Sale in Silicon Valley (Sunnyvale, most likely).