The following is Figure 1 in Gene M. Amdahl's "Validity of the single processor approach to achieving large scale computing capabilities" (1967) (PDF):

Figure 1 from Amdahl's "Validity of the single processor approach"

The text describes this as representing the performance (presumably vertical) as a function of the fraction of instructions that can be executed in parallel for three machines. Machine A has 32 arithmetic execution units, machine B has 3-deep pipelined execution units working on 8-element vectors, machine C has 3-deep pipelined execution units with 8-wide scalar execution (if I understood the descriptions correctly). With a note that "The probable region of operation is centered around a point corresponding to 25% data management overhead and 10% of the problem operations forced to be sequential."

How did Amdahl derive this graph and how is the graph meant to be interpreted?

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    $\begingroup$ In what paper? Please provide both paper and graph. $\endgroup$ – Bartosz Przybylski Feb 7 '14 at 22:13
  • $\begingroup$ It's corrected by Paul, thanks for the edit. I assumed it a very well known paper.. $\endgroup$ – AhlyM Feb 9 '14 at 20:22
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    $\begingroup$ Known or unknown your question should be clear even for people who haven't read it ;) $\endgroup$ – Bartosz Przybylski Feb 9 '14 at 20:29

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