between the one in the Science Museum and this new machine? TFS states "two tons heavier", but the article doesn't mention it, nor the CHM website. The London machine weighs 5.5 tons including its printer, the CHM machine also is listed at 5 tons. What gives? AFAIK, they're identical. I don't think S/N 1 at the Science Museum was ever precisely weighed, but S/N 2 had to be for the air freight shipment. There has also been some confusion over whether the weights were in US or long tons. The most complete sources (Doron's IEEE Annals article, derived from his book) says 5 metric tons, which is 5.5 US tons.
chmguy
I'm am one of the Docents for the Difference Engine #2, and although the team making it work is WAAAAY more competent to comment, lemme put out a few FACTS, at the risk of "flame wars of death"...
The Engine is a single function calculator that can iterate the values of a 7th order polynomial approximation to an arbitrary mathematical function. After about an hour of VERY careful setup, any set of coefficients could be entered, allowing almost any function to realized. It uses a technique called "finite differences" that allows the calculation to be performed using only addition (and 10's compliment coefficients to represent negative numbers). Our working plan is to set it up to do a table of logarithms, much like Babbage's own table, produced well before he thought of Difference Engine #2. The polynomial approximation for logarithms is quite accurate over the space from 1.0 to 1.6, 6000 iterations of the Engine. (It takes four turns of the crank or about 6 sec. per iteration.)
The calculation section has about 4,000 parts, and a very elaborate printer mechanism has another 4,000, and was designed to produce sterotype molds of a complete page of a book of tables.
It is a WONDEROUS device to behold! There are 52 distinct stages in it's control graph (EXACTLY like a modern timing diagram, just vertical...) An elaborate nest of 14 cams control the complex sequence of events to do an iteration, which is !pipelined!. The sinuous ripple carry mechanisms on the back side are HYPNOTIC, as are the forward and backward movements of the intra-column sector gears.
Avoid CHM on May 10, it's gonna be a madhouse! But this is pretty close to the top of the list of "1000 Geeky Things to See Before You Die", oh, and by the way, there's all the other ABSOLUTELY WAY COOL stuff at CHM, wanna see an Apple I signed by "the Woz"...
YOU GOTTA SEE THIS!
chmguy
Slashdot Mirror
chmguy
I'm am one of the Docents for the Difference Engine #2, and although the team making it work is WAAAAY more competent to comment, lemme put out a few FACTS, at the risk of "flame wars of death"... The Engine is a single function calculator that can iterate the values of a 7th order polynomial approximation to an arbitrary mathematical function. After about an hour of VERY careful setup, any set of coefficients could be entered, allowing almost any function to realized. It uses a technique called "finite differences" that allows the calculation to be performed using only addition (and 10's compliment coefficients to represent negative numbers). Our working plan is to set it up to do a table of logarithms, much like Babbage's own table, produced well before he thought of Difference Engine #2. The polynomial approximation for logarithms is quite accurate over the space from 1.0 to 1.6, 6000 iterations of the Engine. (It takes four turns of the crank or about 6 sec. per iteration.)
The calculation section has about 4,000 parts, and a very elaborate printer mechanism has another 4,000, and was designed to produce sterotype molds of a complete page of a book of tables.
It is a WONDEROUS device to behold! There are 52 distinct stages in it's control graph (EXACTLY like a modern timing diagram, just vertical...) An elaborate nest of 14 cams control the complex sequence of events to do an iteration, which is !pipelined!. The sinuous ripple carry mechanisms on the back side are HYPNOTIC, as are the forward and backward movements of the intra-column sector gears.
Avoid CHM on May 10, it's gonna be a madhouse! But this is pretty close to the top of the list of "1000 Geeky Things to See Before You Die", oh, and by the way, there's all the other ABSOLUTELY WAY COOL stuff at CHM, wanna see an Apple I signed by "the Woz"...
YOU GOTTA SEE THIS! chmguy