Re: [tech-aia] RISC-V ACLINT specification is now hosted on RISC-V GitHub


Josh Scheid
 

On Fri, May 28, 2021 at 4:01 PM Greg Favor <gfavor@...> wrote:

More recent ARM SBSA requires a 1 GHz counter resolution, but does not place any requirement on the actual measurable 'time" resolution (i.e. a minimum update frequency).  So one can have 1 ns resolution in the 'time' counter value, but the actual measurable granularity could be just 1 us.

Upping the standard counter resolution seems of little or secondary value.  It's the actual maximum granularity or resolution of measurable time that matters.  Which no one in RISC-V (or ARM SBSA) seems willing or wanting to require actual 1 ns resolution to time measurements.


Right, I'm attempting to refer to the effective timer resolution as opposed to the apparent timer unit period.

I'm just making explicit what this relaxation implies about capabilities in real systems.  Platforms should separately consider whether or not to allow this relaxation based on a threshold for effective timer resolution which must be available on compliant implementations of that platform.

-Josh

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