60-bit computing

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In computer architecture, 60-bit integers, memory addresses, or other data units are those that are 60 bits wide. Also, 60-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers, address buses, or data buses of that size.

60-bit CDC 6600 introduced in 1964

A 60-bit word is typically used for high-precision floating-point calculations; it can also store 10 6-bit characters.[1]


The only widely-used computers with 60-bit words were produced by Control Data Corporation (CDC),[2] including the CDC 6000 series,[3] the CDC 7600, and the CDC Cyber 70 and 170 series.[4] Though the addressable unit was the 60-bit word, instructions were either 15 or 30 bits.[3]

Early design documents for the IBM 7030 Stretch tentatively specified its word length as 60 bits; the final design used 64.[5]


Museum examples of 60-bit CDC machines exist. There also exists an emulator for the series which will simulate the CDC 60-bit machines on commodity hardware and operating systems.[4]


  1. ^ James L. Peterson, Computer Organization and Assembly Language Programming, 2014, ISBN 1483268594, p. 46
  2. ^ Peterson; Concise Encyclopedia of Computer Science, 2004 ISBN 0470090952; Linda Null, Julia Lobur, Essentials of Computer Organization and Architecture, 2014, ISBN 1284033155; John Y. Hsu, Computer Architecture: Software Aspects, Coding, and Hardware, 2017, ISBN 1351836048
  3. ^ a b "CDC 6000 Hardware". 60bits.net. Central Memory. Archived from the original on 28 February 2019. Retrieved 28 February 2018.
  4. ^ a b "Welcome to cray-cyber.org - home of Cray Research and CDC computer". Desktop Cyber. Archived from the original on 28 February 2019. Retrieved 28 February 2018.
  5. ^ Werner Buchholz, "Memory Word Length", STRETCH Memo no. 40, July 31, 1956, archived at the Computer History Museum