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| author | Paul Donahue <48959409+pdonahue-ventana@users.noreply.github.com> | 2024-02-06 16:33:37 -0800 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2024-02-06 16:33:37 -0800 |
| commit | de72062b6b37b3fe5bdc703c4bb24f0b798c6d7b (patch) | |
| tree | dee850c340e75004146ae7c0ebd29efbe886a617 /src/counters.adoc | |
| parent | 40821cd5c933d9242bc4ab77ca99c46613f0f473 (diff) | |
| download | riscv-isa-manual-de72062b6b37b3fe5bdc703c4bb24f0b798c6d7b.zip riscv-isa-manual-de72062b6b37b3fe5bdc703c4bb24f0b798c6d7b.tar.gz riscv-isa-manual-de72062b6b37b3fe5bdc703c4bb24f0b798c6d7b.tar.bz2 | |
Don't conflate hart and system (#1215)
* Add clarifying non-normative comments about [m]time
Text contributed by @gfavor
* Don't conflate hart and system
* Don't conflate hart and system
* Remove text that mysteriously appeared on my branch.
---------
Co-authored-by: Andrew Waterman <andrew@sifive.com>
Diffstat (limited to 'src/counters.adoc')
| -rw-r--r-- | src/counters.adoc | 16 |
1 files changed, 0 insertions, 16 deletions
diff --git a/src/counters.adoc b/src/counters.adoc index 2011386..cf646c6 100644 --- a/src/counters.adoc +++ b/src/counters.adoc @@ -147,22 +147,6 @@ As with other architectural mandates, it suffices to appear "as if" harts are synchronized to within one tick of the real-time clock, i.e., software is unable to observe that there is a greater delta between the real-time clock values observed on two harts. - -If, for example, the real-time clock increments at a frequency of 1 GHz, then -all harts must appear to be synchronized to within 1 nsec. -But it is also acceptable for this example implementation to only update the -real-time clock at, say, a frequency of 100 MHz with increments of 10 ticks. -As long as software cannot observe this seeming violation of the above -synchronization requirement, and software always observes time across harts to -be monotonically nondecreasing, then this implementation is compliant. - -A platform spec may then, for example, specify an apparent real-time clock -tick frequency (e.g. 1 GHz) and also a minimum update frequency (e.g. 100 MHz) -at which updated time values are guaranteed to be observable by software. -Software may read time more frequently, but it should only observe -monotonically nondecreasing values and it should observe a new value at least -once every 10 ns (corresponding to the 100 MHz update frequency in this -example). ==== The RDINSTRET pseudoinstruction reads the low XLEN bits of the `instret` CSR, which counts the number of instructions retired by this |