CDC 6600 Links

(replace later with more professional photos)

CDC circuit boards - top view

CDC circuit boards - side view

Left - single board similar to those used in earlier CDC computers
Middle - cordwood module similar to those used in the 6000 series
Right - eight-board module similar to those used in the 7600 (this particular module may be from a Cyber 175; the covers have been removed for this photo; the transistors are the small gray dots)

Note on the transistors used

Seymour Cray of Control Data Corporation awarded Fairchild a development contract for a silicon transistor that switched in less than 3 nanoseconds (ns). Existing silicon transistors offered operation superior to germanium at the elevated ambient temperatures prevalent in large computers but were too slow for Cray's planned new model 6600 supercomputer. Jean Hoerni met CDC's demanding specification by combining gold-doping - the addition of gold impurities (a technique he had developed for use on the company's original product line in 1959) - together with the new epitaxial deposition process. The 2N709 NPN device was introduced in July 1961 as the first silicon transistor to exceed germanium speed. In 1964, CDC placed "one of the largest single orders in the history of the semiconductor industry" with Fairchild for more than 10 million of the devices.

David Laws, "A Company of Legend: The Legacy of Fairchild Semiconductor," IEEE Annals of the History of Computing, 32(1), 2010, pp. 60-74.

See also section IV.F, "A 1960 Supercomputer Design and a Missle Using Silicon Planar Transistors," in C.T. Sah, "Evolution of the MOS Transistor: From Conception to VLSI," Proceedings of the IEEE, 76(10) 1988, pp. 1280-1326.

Note on lack of I/O interrupts

Please see the CDC 6600 section in my history of interrupts page.

I/O programming for a PPU is discussed on pages 4-37 through 4-39 of the Control Data 6400/6500/6600 Computer Systems Reference Manual.

CDC 6500 running in 2016 at Living Computers Museum + Labs

After the introduction of the 6600, CDC produced a lower cost model 6400 with a sequential CPU and a model 6500 with two sequential processors. The 6500 at LCM is the one used at Purdue University from 1967 to 1989.

participants at CDC reunion at LCM
Paul Allen and Joe Cychosz are third and second from right, respectively
a recently built module and an original module
LCM fabricated replacement cordword modules
inserting a cordwood module in CDC 6500 at LCM
[photos courtesy of LCM and]

See also the video interview of Lath Carlson at LCM by Geek Wire

Subsequent Models

The Cyber 70 series (ca. 1971) added a number of features to the CDC 6600 instruction set and used faster and cheaper discrete transistors. The Cyber 72 was an update of the CDC 6200; the Cyber 73 was an update of the CDC 6400; and, the Cyber 74 was an update of the CDC 6600.

Most of the models in the Cyber 170-1xx series (ca. 1973) used up to sixteen 16-pin ECL DIP chips instead of discrete transistors within a cordwood logic module so that the same type of frames and cooling could continue to be used. The diagram below is from this CDC training manual on Bitsavers.

line drawing of a 170 cordwood module
See a picture of a Cyber 170 module here. I believe that this picture from the CDC photograph archives at CBI compares a memory stack from the CDC 6600 with Cyber 170 memory modules. [I believe that the description as "logic" is incorrect. See also this picture that compares several different implementation families.]

Lloyd Thorndyke describes a foot-square LSI gate array version of the CDC 6400 built by CDC Research ca. 1974 on page 25 in his oral history interview with Dag Spicer in 2010. Unfortunately, an executive required that an instruction (or two) be left out of the design, and that omission was later used to discredit the successful implementation. Tony Vacca gives additional details about the implementation effort in the section entitled "Addendum 1 - The test vehicle that validated CAD" in his ETA-10 article on the Engineering Technology and History Wiki. [I believe he means 1974 rather than 1984 in his addendum.]

See chapter 7 of John Vardalas, The Computer Revolution in Canada: Building National Technological Competence, MIT Press, 2001, for a discussion of CDC-Canada's efforts on the Cyber 173.

Note: The Cyber 76 was an update of the CDC 7600, and the Cyber 175 and 176 were updates of the Cyber 76. See the 1975 Cyber 170 Systems Hardware Handbook on Bitsavers for more information.

Acknowledgement: My thanks to Joe Cychosz for his help with CDC and Cray hardware details and for alerting me to the 2016 event at LCM.

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