HPET vs other timers

Poul-Henning Kamp phk at phk.freebsd.dk
Sat Jun 2 21:15:23 UTC 2007

In message <20070602194151.GA1604 at rot13.obsecurity.org>, Kris Kennaway writes:

>> Anyone able to speculate why though?  HPET only reads 32 bits from a
>> memory mapped region.  No locking or other requirements.  ACPI_timer
>> does multiple IO ops, which according to bde@ are much slower than
>> memory reads.  

HPET needs to do metastability mitigation and is not "just a read
from a memory mapped region".

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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