Home / Destinations / San Francisco / Computer History Museum / The checkable facts
Computer History Museum — The checkable facts
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.
| Claim | Source |
|---|---|
| Difference Engine No. 2 has 8,000 parts, weighs five tons and measures 11 feet long | Computer History Museum — About the museum |
| The first complete Babbage engine was finished in London in 2002, 153 years after it was designed | Computer History Museum — About the museum |
| The engine was on loan from Nathan Myhrvold from 2008 and on display until 31 January 2016 | Computer History Museum — The Babbage Engine |
| The museum holds a restored PDP-1, two restored IBM 1401s and a restored IBM RAMAC 350 disk drive | Computer History Museum — The Babbage Engine |
| The collection includes an example of the first generation of Google's custom-designed web server racks | Computer History Museum — The Babbage Engine |
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.
Sixty seconds costs nothing
Judge the writing and the voice before you spend anything.