Editing Control Data Corporation (section)

== CDC 7600 and 8600 ==
[[File:CDC 7600.jc.jpg|thumb|CDC 7600, serial no. 1]]
{{main|CDC 7600|CDC 8600}}

In the same month it won its lawsuit against IBM, CDC announced its new computer, the [[CDC 7600]]<ref>{{cite book
|title=ACHIEVING ACCURACY: A Legacy of Computers and Missiles |url=https://books.google.com/books?isbn=1462810659
|isbn=978-1-4628-1065-9  |author=Marshall William McMurran  |date=2008| publisher=Xlibris Corporation }}</ref> (previously referred to as the 6800 within CDC). This machine's hardware clock speed was almost four times that of the 6600 (36&nbsp;MHz vs. 10&nbsp;MHz), with a 27.5 [[nanosecond|ns]] clock cycle, and it offered considerably more than four times the total throughput, with much of the speed increase coming from extensive use of [[instruction pipeline|pipelining]].

The 7600 did not sell well because it was introduced during the 1969 downturn in the U.S. national economy. Its complexity had led to poor reliability. The machine was not totally compatible with the 6000-series and required a completely different [[operating system]], which like most new OSs, was primitive. The 7600 project paid for itself, but damaged CDC's reputation. The 7600 memory had a split primary- and secondary-memory which required user management but was more than fast enough to make it the fastest uniprocessor from 1969 to 1976. A few dozen 7600s were the computers of choice at supercomputer centers around the  world.

Cray then turned to the design of the [[CDC 8600]]. This design included four 7600-like processors in a single, smaller case. The smaller size and shorter signal paths allowed the 8600 to run at much higher clock speeds which, together with faster memory, provided most of the performance gains. The 8600, however, belonged to the "old school" in terms of its physical construction, and it used individual components [[soldering|soldered]] to [[circuit board]]s. The design was so compact that cooling the CPU modules proved effectively impossible, and access for maintenance difficult. An abundance of hot-running solder joints ensured that the machines did not work reliably; Cray recognized that a re-design was needed.