[ntp:questions] Linux 11-minute mode (RTC update)

Maciej W. Rozycki macro at linux-mips.org
Thu Apr 10 16:20:21 UTC 2008

On Wed, 9 Apr 2008, Unruh wrote:

> WHAT? What linux platform uses the "1 interrupt per second" of the rtc
> clock as the timer interrupt? (never mind that the latest motherboards do
> not have an rtc at all, and use the HPET in poll mode to mimic an rtc).

 A number of DEC platforms have their RTC chip (a Dallas 1287A typically) 
as the only source of the timer interrupt.  The rate is configurable in 
powers of two between 2Hz and 8192Hz, with 128Hz and 1024Hz being the 
commonest with Linux (and elsewhere).  You must be confusing the 
update-ended interrupt (which is indeed 1Hz) here with the periodic 
interrupt which may be set to the desired rate.


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