Silicon Valley's latest computer was recently unveiled, but the entrepreneur who designed it missed the event by 137 years. Charles Babbage, an English mathematician, did the R&D on his Difference Engine No. 2 in 1847 and died in 1871. But none actually existed until 2002 at London's Science Museum.

This is the second one, on display starting May 10 at the Computer History Museum in Mountain View, California. It was built for the private collection of former Microsoft executive Nathan Myhrvold, (MER-vohld) who helped finance the completion of the Science Museum's device.

The Difference Engine has 8,000 moving parts and weighs five tons. It would cost $2.5 million to build another one, according to Doron Swade (DOR-un "swayed"), the guest curator from the London Science Museum. But it does calculations that it would take a 64-bit processor to do in one cycle.

Babbage designed the engine because of fears about errors in printed mathematical tables.

SWADE: "Anyone who did a calculation that was non-trivial relied on printed mathematical tables. ... These tables were calculated by hand, by humans, humans make mistakes."

Babbage designed the Engine to crank out tables as needed, without errors.

SWADE: "You can't ask it to multiply two numbers and produce a result. Whatever numbers you put into it, it crunches the only way it knows how, which is the method of finite differences, which is repeated addition. But what that allows you to do is to calculate the value of a polynomial."

Polynomials were the key to producing the values in those tables, which were used in navigation, science, and engineering. They had to be very precise and today's calculators don't go to this many digits. Desktop computers can do the job, but the Difference Engine had a feature that would have been critical in its time.

"So you turn the handle, and it calculates the result. It also prints it and sterotypes the result. So it impresses the results, 30 digits of them, into soft material, plaster of Paris, for example, from which you can cast a printing plate for use in a conventional printing press."

All without the need for human transcription. But the Victorians never got one.

SWADE: "In Babbage's time, his designs were a quantum leap in logical complexity and physical size. ... Babbage designed huge calculating engines, but he failed to build any in his lifetime. ... He failed for various reasons, including personality, finance, all sorts of other things, a walkout by his chief engineer."

Myhrvold said he commissioned the project because Silicon Valley spends too much time looking forward, and not enough looking back.

MYHRVOLD: "If you're trying to figure out what the next great thing is, you have two choices. You can just blankly try it, or you can try to learn something from history."

In at least one respect, Difference Engine No. 2 is the perfect computer for today.

SWADE: "Is it a green machine? Yep! It's operated by turning a handle. ... it has no carbon footprint, except, I mean, if you exclude the manufacture of the metals."

For the IDG News Service, I'm Nick Barber in Boston, with reporting by Stephen Lawson, in Mountain View, California.