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Computer History Museum

Quick answer

The Computer History Museum in Mountain View, California holds the largest collection of computing artifacts in the world, including one of three working DEC PDP-1 machines, an IBM 1401 restored over roughly a decade by retired IBM engineers, a Cray-1, an Apple I, and Google's first production server. A working Babbage Difference Engine No. 2 was demonstrated there from 2008 to 2016.

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The Machine Babbage Never Built

Charles Babbage designed a mechanical calculating engine in the eighteen forties. He drew it in obsessive detail and he never finished building one. For a century and a half it was a famous might have been. The Science Museum in London finally built one in 2002, 153 years after it was drawn. From 2008 until the 31st of January, 2016, this museum had it on loan from Nathan Myhrvold, built from Babbage's original drawings with no design changes. It is 8,000 parts, five tons and 11 feet long, and it computes. Visitors who caught it watched a docent turn the crank and saw a Victorian idea execute; the machine has since gone back to its owner. It is the single best argument in this building that computing is older than electricity, and most visitors walk past it looking for the iPhones.

Three Working PDP-1s

Somewhere in this building is one of three working PDP-1 computers left on earth. It is from 1959, it cost about a hundred and twenty thousand dollars, and it has a round screen. On that screen the museum runs Spacewar, written in 1962 by students at MIT — arguably the first real video game, made because someone wanted to show off what the machine could do. Volunteers demonstrate it, and sometimes you get to play. Nearby is an IBM 1401, the machine that put computing into ordinary businesses in the nineteen sixties. It was restored over about ten years by a team of volunteers, many of them retired IBM engineers who had originally serviced these machines. They brought back the hardware they built their careers on, and it prints.

The First Google Server

Also here: Google's first production server. Not a rack — a stack of bare boards on a frame, held together with the cheapest materials that would work, because two graduate students needed disk space more than they needed dignity. That is the real lesson of this museum, and the reason it belongs in this valley rather than in Washington. Almost nothing here looks impressive at the moment it was made. The Cray one supercomputer looks like furniture. The Apple one is a bare board. One practical thing: **check the demonstration schedule the moment you walk in.** The PDP-1 and the IBM 1401 only run at specific times with volunteers present, and those two demonstrations are the reason to come here rather than read about it. Plan the rest of your visit around them.

The checkable facts

  • Difference Engine No. 2 has 8,000 parts, weighs five tons and measures 11 feet long
  • The first complete Babbage engine was finished in London in 2002, 153 years after it was designed
  • The engine was on loan from Nathan Myhrvold from 2008 and on display until 31 January 2016
  • The museum holds a restored PDP-1, two restored IBM 1401s and a restored IBM RAMAC 350 disk drive

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Frequently asked

What does a difference engine actually do?
It evaluates polynomial expressions by repeated addition, which lets it generate mathematical tables without a human calculator. The design carries numbers to 31 decimal digits and includes a printing apparatus that presses results into a soft plate, removing typesetting mistakes as well as arithmetic ones. Every operation is mechanical, with no electricity involved anywhere.
Can you see the PDP-1 running?
Only at scheduled demonstration times, when trained volunteers power it up. The machine dates from 1959, uses a circular cathode ray display, and runs Spacewar!, written at MIT in 1962. Sessions are short and the room holds few people, so the schedule posted at the entrance decides whether a visit includes it.
Why is Google's first server in a museum?
Because it records a design decision rather than an achievement. Instead of buying reliable server hardware, the founders stacked commodity boards on open frames and made the software tolerate failure, which is how search scaled cheaply. The hardware reached the museum as part of a donation of early material from the company.
How long did the IBM 1401 restoration take?
Roughly a decade of weekly work by a volunteer team, many of them retired IBM field engineers who had maintained the same model in service. They rebuilt the card reader, the chain printer and the core memory, sourcing components that had not been manufactured for fifty years. The machine prints during demonstrations.
Where is the Computer History Museum?
Mountain View, in Silicon Valley, roughly 40 miles south of downtown San Francisco on North Shoreline Boulevard. It occupies a building that opened as the museum's home in 2002, previously the headquarters of Silicon Graphics. Driving takes about an hour from the city in ordinary traffic; Caltrain plus a shuttle is the transit route.

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