[math-fun] Geoff Tootill obituary: factored 2^18
FYI -- The Guardian doesn't usually screw up scientific/technical/mathematical things, but mathematically mature babies are rolling their eyes... Perhaps it was 2^18-1 ? 2^18+1 ? BTW, if the total instruction store only holds 32 instructions, how complex could the program be? How long could the longest-running program that *halts* run (in terms of program steps) ? https://www.theguardian.com/global/2017/nov/08/geoff-tootill-obituary Geoff Tootill obituary Computer engineer who developed 'Baby', the world's first stored-program computer Martin Campbell-Kelly Wednesday 8 November 2017 15.53 GMT ... In order to test the memory when it was constructed, Kilburn and Tootill designed an elementary computer, officially known as the Small-Scale Experimental Machine, but better known as "Baby". The computer could store just 32 instructions or numbers using a single cathode ray tube. The machine first worked in June 1948, taking 52 minutes to find the highest factor of 2^18, involving about 3.5m arithmetic operations. ---- Even less forgivable, *SlashDot* also screwed this one up: https://hardware.slashdot.org/story/17/11/26/197221/computer-pioneer-geoff-t...
Perhaps it was 2^18-1 ? 2^18+1 ?
No. It was indeed finding "the highest proper divisor" of 2^18 (i.e. 131072). The only arithmetic operations implemented in hardware were subtraction and negation. Divisions had to be implemented by repeated subtractions of the divisor. "The machine was not intended to be a practical computer but was instead designed as a testbed for the Williams tube, an early form of computer memory." http://www.historyofinformation.com/expanded.php?id=858 Alas, 2^18 is written there as 218.
Thx for the clarification! Was "Baby" a decimal machine? BTW, didn't Minsky prove that subtraction & test for zero was universal? At 12:40 PM 11/26/2017, Hans Havermann wrote:
Perhaps it was 2^18-1 ? 2^18+1 ?
No. It was indeed finding "the highest proper divisor" of 2^18 (i.e. 131072). The only arithmetic operations implemented in hardware were subtraction and negation. Divisions had to be implemented by repeated subtractions of the divisor. "The machine was not intended to be a practical computer but was instead designed as a testbed for the Williams tube, an early form of computer memory."
http://www.historyofinformation.com/expanded.php?id=858
Alas, 2^18 is written there as 218.
yes, machines with two or more integer counters that can increment, decrement, and branch on zero are universal. - Cris
On Nov 26, 2017, at 1:50 PM, Henry Baker <hbaker1@pipeline.com> wrote:
BTW, didn't Minsky prove that subtraction & test for zero was universal?
Cristopher Moore Professor, Santa Fe Institute Why should we be deported? This is very, very hard for a family. What will our fellow citizens think if honest subjects are faced with such a decree — not to mention the great material losses it would incur. I would like to become a Bavarian citizen again. Your most humble and obedient, Friedrich Trump (1905)
I guess this is no worse than the first quantum computer which Shor-factored 15=3*5. At 12:40 PM 11/26/2017, Hans Havermann wrote:
Perhaps it was 2^18-1 ? 2^18+1 ?
No. It was indeed finding "the highest proper divisor" of 2^18 (i.e. 131072). The only arithmetic operations implemented in hardware were subtraction and negation. Divisions had to be implemented by repeated subtractions of the divisor. "The machine was not intended to be a practical computer but was instead designed as a testbed for the Williams tube, an early form of computer memory."
http://www.historyofinformation.com/expanded.php?id=858
Alas, 2^18 is written there as 218.
participants (3)
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Cris Moore -
Hans Havermann -
Henry Baker