The CADET was in fact the IBM 1620, contemporaneous with the IBM 1401, but more for 'scientific' market. The '1620 uses these clever in-core tables and iterati

The CADET was in fact the IBM 1620, contemporaneous with the IBM 1401, but more for 'scientific' market. The '1620 uses these clever in-core tables and iteration to achieve arbitrary-precision addition/subtraction and different tables for multiplication/division; I implemented the algo in C and it worked great, certainly fast enough for the occasional arb-precision computation. The IBM 1401 could operate on arbitrary strings of digits in hardware ; since that was my first machine, I was disappointed when I used these silly 'binary' machines. However, a typical instruction + operand fetch/store took about 100 microseconds on the '1401; yes, that is 10 kilo-instructions per second! There were many programming tricks to minimize instruction fetch e.g.'chaining' instructions, using left-over contents of the regs in the next instr, and using parts of instr as data, the most common being: "A *-6,FOO" because "*-6" is relative address, which points to the letter 'A', which was BCD +1, etc. Equivalent to ++FOO; The pdp-11/45 I used next took about 2.5 usec per instruction with 2 memory operands -- 400 kilo instructions per second! This "40x" speedup of the 11/45 over the IBM 1401 more than compensated for the hardware arbitrary-precision addition/subtraction! (oh, and on the '1401, the HW 'Multiply/Divide Feature' was another big group of electronic cards, if you bought that) http://ed-thelen.org/comp-hist/ibm-1401.html http://ed-thelen.org/comp-hist/ibm-1401.html (edit: learned that \* needed to not have * gobbled by the markdown italics sentinel https://news.ycombinator.com/formatdoc https://news.ycombinator.com/formatdoc)