instruction timings (was: Assembly or ....)

[Doug Gwyn]

In article <960 at vsi.COM> friedl at vsi.COM (Stephen J. Friedl) writes:
>Why is this?  When I was hacking on the VAX, nobody could ever
>tell me how long anything took, and empirical measurements were
>pretty tedious.  Is it laziness on the vendor's part or are there
>good reasons for this?

Exact computations of instruction timings, already quite difficult
for the VAX-11/780, have become so context-dependent as to be not
worth attempting.  Time taken for a given instruction depends on
such things as cache hit rate, fault rate, instruction mix, and so
forth.  What really matters is overall system performance, which
is a statistical matter.