svn commit: r274739 - head/sys/mips/conf

[Mark R V Murray]

> On 25 Nov 2014, at 07:59, Warner Losh <imp at bsdimp.com> wrote:
> 
> 
>> On Nov 25, 2014, at 12:57 AM, Mark R V Murray <mark at grondar.org> wrote:
>> 
>> 
>>> On 24 Nov 2014, at 23:22, Warner Losh <imp at bsdimp.com> wrote:
>>> 
>>> What’s the minimum specs required for get_cyclecount()? Not all of the
>>> boxes that Ian was posting about have high-resolution time-keeping counters
>>> in hardware… Maybe there’s some underlying expectation for this function
>>> that these systems either aren’t providing or can’t provide.
>> 
>> get_cyclecount should be a high-resolution timing counter linear in time, with a minimum tick no more accurate than a single instruction execution. In practice we take what we can get. It is used to measure hopefully chaotic events in order to obtain environmental entropy.
> 
> So right. armv6 and mips have something akin to that, but IIRC, not all arm v4/5 boxes can do much better than microseconds…

That’s my understanding. I still don’t get the massive differences; they should be tiny.

M
-- 
Mark R V Murray