Editing Clock rate (section)

== Research ==
Engineers continue to find new ways to design CPUs that settle a little more quickly or use slightly less energy per transition, pushing back those limits, producing new CPUs that can run at slightly higher clock rates. The ultimate limits to energy per transition are explored in [[reversible computing]].

The first fully reversible CPU, the Pendulum, was implemented using standard CMOS transistors in the late 1990s at the Massachusetts Institute of Technology.<ref>
{{Cite web |last=Frank |first=Michael |title=The Reversible and Quantum Computing Group (Revcomp) |url=https://www.cise.ufl.edu/research/revcomp/ |access-date=2024-03-17 |website=www.cise.ufl.edu}}
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{{Cite web |last=Swaine |first=Michael |date=2004 |title=Backward to the Future |url=http://www.drdobbs.com/backward-to-the-future/184405563 |access-date=2024-03-17 |website=Dr. Dobb's}}
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Michael P. Frank. [http://www.zettaflops.org/PES/frank.html "Reversible Computing: A Requirement for Extreme Supercomputing"].
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Matthew Arthur Morrison. [http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=6278&context=etd "Theory, Synthesis, and Application of Adiabatic and Reversible Logic Circuits For Security Applications"]. 2014.
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Engineers also continue to find new ways to design CPUs so that they complete more instructions per clock cycle, thus achieving a lower [[cycles per instruction|CPI]] (cycles or clock cycles per instruction) count, although they may run at the same or a lower clock rate as older CPUs. This is achieved through architectural techniques such as [[instruction pipelining]] and [[out-of-order execution]] which attempts to exploit [[instruction level parallelism]] in the code.