Editing Simultaneous multithreading (section)

== Historical implementations ==
While multithreading CPUs have been around since the 1950s, simultaneous multithreading was first researched by IBM in 1968 as part of the [[ACS-1|ACS-360]] project.<ref>{{cite web |url=http://people.cs.clemson.edu/~mark/acs_end.html |title=End of IBM ACS Project |first=Mark |last=Smotherman |date=25 May 2011 |access-date=January 19, 2013 |publisher=School of Computing, Clemson University}}</ref> The first major commercial microprocessor developed with SMT was the [[Alpha 21464]] (EV8). This microprocessor was developed by [[Digital Equipment Corporation|DEC]] in coordination with Dean Tullsen of the University of California, San Diego, and Susan Eggers and Henry Levy of the University of Washington. The microprocessor was never released, since the Alpha line of microprocessors was discontinued shortly before [[Hewlett-Packard|HP]] acquired [[Compaq]] which had in turn acquired [[Digital Equipment Corporation|DEC]]. Dean Tullsen's work was also used to develop the [[hyper-threading|hyper-threaded]] versions of the Intel Pentium&nbsp;4 microprocessors, such as the "Northwood" and "Prescott".