ARM made a clockless chip in 1994 for cellphones. Couldn't find an amazing reference, but a quick google turned up http://www1.cs.columbia.edu/async/misc/technologyr eview_oct_01_2001.html where they briefly mention it... The last time I heard of this stuff being used was in 2001-- I actually wrote an English paper about it purely to see if I could bore my professor :-p