Re: Ada.Execution_Time

["(see below)" <news@findlayw.plus.com>]

At least part of this discussion is motivated by the abysmal facilities for
the measurement of elapsed time on some (all?) modern architectures.

My current Ada project is the emulation of the KDF9, a computer introduced
50 years ago. It had a hardware clock register that was incremented by 1
every 32 logic clock cycles and could be read by a single instruction taking
4 logic clock cycles (the CPU ran on a 1MHz logic clock).

Using this feature, the OS could keep track of the CPU time used by a
process to within 32 logic clock cycles per time slice (typically better
than 1 part in 1_000). Summing many such slices gives a total with much
better relative error than that of the individual slices, of course.

Dmitri reports a modern computer with a timer having a resolution that is
thousands or millions of times worse than the CPU's logic clock.

Why has this aspect of computer architecture degenerated so much, I wonder?
And why have software people not made more of a push for improvements?

-- 
Bill Findlay
with blueyonder.co.uk;
use  surname & forename;