Editing Transputer (section)

=== Architecture ===
The original transputer used a very simple and rather unusual architecture to achieve a high performance in a small area. It used [[microcode]] as the main method to control the data path, but unlike other designs of the time, many instructions took only one cycle to execute. Instruction [[opcode]]s were used as the entry points to the microcode [[read-only memory]] (ROM) and the outputs from the ROM were fed directly to the data path. For multi-cycle instructions, while the data path was performing the first cycle, the microcode decoded four possible options for the second cycle. The decision as to which of these options would actually be used could be made near the end of the first cycle. This allowed for very fast operation while keeping the architecture generic.<ref>Stakem, Patrick H. The Hardware and Software Architecture of the Transputer, 2011, PRB Publishing, ASIN B004OYTS1K</ref>

The [[clock rate]] of 20&nbsp;MHz was quite high for the era and the designers were very concerned about the practicality of distributing such a fast clock signal on a board. A slower external clock of 5&nbsp;MHz was used, and this was multiplied up to the needed internal frequency using a [[phase-locked loop]] (PLL). The internal clock actually had [[clock signal#4-phase clock|four non-overlapping phases]] and designers were free to use whichever combination of these they wanted, so it could be argued that the transputer actually ran at 80&nbsp;MHz. [[Dynamic logic (digital electronics)|Dynamic logic]] was used in many parts of the design to reduce area and increase speed. Unfortunately, these methods are difficult to combine with [[automatic test pattern generation]] scan testing so they fell out of favour for later designs.

Prentice-Hall published a book<ref>{{cite book|url=http://www.transputer.net/ibooks/72-trn-006-04/trefm04.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.transputer.net/ibooks/72-trn-006-04/trefm04.pdf |archive-date=2022-10-09 |url-status=live|title=Transputer Reference Manual|publisher=[[Prentice-Hall]]|date=1988|isbn=0-13-929001-X}}</ref> on the general principles of the transputer.