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          Hand wired Memory!

    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.
Front of hand wired memory board
Click photo to enlarge
    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!
Back of hand wired memory board
Click photo to enlarge
    The close up gives a better idea of the patience required... and of the motivation that drove this hobbyist, in those early days of the home computer revolution. These days, when you can buy a Gigabyte of memory in a tiny card for a pittance, it's hard to remember that these 24 Kilobytes were once a prize worth slaving for...
Chips on hand wired memory board  Wire wrapped pins on hand wired memory board
Click a photo to enlarge
Exhibit provenance:
    As I said, a Garage Sale in Silicon Valley (Sunnyvale, most likely).
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