Basic HTML version of Foils prepared 17 November 98

Foil 12 What is a Pipeline -- Cafeteria Analogy?

From Master Foilset for HPC Achitecture Overview CPS615 Introduction to Computational Science -- Fall Semester 1998. by Geoffrey C. Fox


Familiar from such everyday activities as getting food in cafeteria where one processes one person per "clock cycle" where
clock cycle here is maximum time anybody takes at a single "stage" where stage is here component of meal (salad, entrée etc.)
Note any one person takes about 5 clock cycles in this pipeline but the pipeline processes one person per clock cycle
Pipeline has problem if there is a "stall" -- here that one of the people wants an entrée which needs to be fetched from kitchen. This delays everybody!
In computer case, stall is caused typically by data not being ready for a particular instruction



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