Editing Digital electronics (section)

===Computer design===
[[File:80486dx2-large.jpg|thumb|Intel 80486DX2 [[microprocessor]]]]

The most general-purpose register-transfer logic machine is a [[computer]]. This is basically an [[automaton|automatic]] binary [[abacus]]. The [[control unit]] of a computer is usually designed as a [[microprogram]] run by a [[microsequencer]]. A microprogram is much like a player-piano roll. Each table entry of the microprogram commands the state of every bit that controls the computer. The sequencer then counts, and the count addresses the memory or combinational logic machine that contains the microprogram. The bits from the microprogram control the [[arithmetic logic unit]], [[memory]] and other parts of the computer, including the microsequencer itself. In this way, the complex task of designing the controls of a computer is reduced to the simpler task of programming a collection of much simpler logic machines.

Almost all computers are synchronous. However, [[asynchronous computer]]s have also been built. One example is the [[ASPIDA DLX]] core.<ref name=aspida>{{cite web|title=ASODA sync/async DLX Core|url=http://opencores.org/project,aspida|website=OpenCores.org|access-date=September 5, 2014}}</ref> Another was offered by [[ARM Holdings]].<ref name=arm-asynch/> They do not, however, have any speed advantages because modern computer designs already run at the speed of their slowest component, usually memory. They do use somewhat less power because a clock distribution network is not needed. An unexpected advantage is that asynchronous computers do not produce spectrally-pure radio noise. They are used in some radio-sensitive mobile-phone base-station controllers.<!--that's quite a noun stack--> They may be more secure in cryptographic applications because their electrical and radio emissions can be more difficult to decode.<ref name=arm-asynch>{{cite web|last1=Clarke|first1=Peter|title=ARM Offers First Clockless Processor Core|url=http://www.eetimes.com/document.asp?doc_id=1299083|website=eetimes.com|publisher=UBM Tech (Universal Business Media)|access-date=5 September 2014}}</ref>