Knex computer at Olin College (knexcomputer.blogspot.com)

13 points by s_baar ↗ HN
"The K'NEX calculator stands over 10 feet tall, and can perform 4 bit addition and subtraction operations in about 30 seconds. The slowest part of the operation is the user entering the balls. From there the balls trickle down, computing the result of the operation, and then sending that through a 4 bit decoder, which flips a flag that tells the user the answer. Since it is 4 bit, we can add and subtract numbers from 0 to 15."

2 comments

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Those things were once cutting-edge; I believe Charles Babbage designed one in the 1830s, and Richard Feynman worked on another mechanical computer in WW2.