Hardware fan uses 55-year-old IBM mainframe to mine bitcoins

Ken Shirriff, a hardware enthusiast, has attempted to mine bitcoins with an IBM Model 1401 mainframe that runs on punched cards. It worked, but it takes patience: it takes more time to compute a single block of hashes than the lifetime of the universe.

Shirrif attempted to run the sha256 algorithm used for bitcoin mining on the 1959 IBM Model 1401. This algorithm is optimized for systems that can handle 32-bit operations, but the IBM 1401 can’t even operate with bytes: the device works on the basis of 6-bit characters. He therefore had to work with 1 character per bit using the assembly programming language for the required translation. In the eyes of the hardware enthusiast, the old mainframe is actually the worst possible system for mining bitcoins.

This is also reflected in the required computation time: the Model 1401 – from a computer museum in California – could in practice calculate a hash every 80 seconds. With that computing speed, the system would take 5×1014 years to mine a 1MB block. That is about 40,000 times the current age of the universe. The electricity bill is also not good: the mainframe burns 3000W, so that the costs would be about 1018 dollars. The proceeds would be 25 bitcoins, approximately 5400 euros at the time of writing.