October 18th, 2010 ~ by admin

Before the PC, Before Apple, was the Xerox Alto

Xerox Alto-II XM

Just last month an Apple 1 computer sold on eBay for almost $23,000. Today, the father of the PC, and where Steve Jobs got many of his inspirations (as did Bill Gates and numerous other founders of the computer industry), sold on eBay for a bit over $30,000.

The Xerox Alto was really the first modern computer as we know it.  It was developed at the PARC research center, and had Ethernet, a mouse, a GUI, and assorted other things we are rather use to now.  The date? 1973. Xerox did not understand the significance of what they had.  They made over 2000 Altos of various configurations, but never sold them, most were simply given away to friends, workers, and universities.

Though never sold, the Alto’s value in the 1970s was $32,000  or so, not a far cry (disregarding inflation) of what a non-working one just sold for on eBay

The Alto was powered by a custom16-bit bit-slice processor consisting of 4 TTL 74181 ALU’s one of the first uses of the 74181, which was itself the first single chip ALU.

TI SN74S181N - Late 1973 - 90MHz

The 74181 consisted of around 75 gates, and could perform 16 arithmetic functions and 16 logic functions on a pair of 4-bit inputs.  It was, for its time, very fast, much faster then most of the single chip processors of the time.  A 74S181 like shown here, using Schottky technology, could operate at up to 90MHz or so.  Obviously in a computer like the Alto actual clock speed would be reduced to match what the memory could do, which in the Alto, with its 128K of RAM, worked out to 5.8MHz.

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