Re: Hardware Clock

FROM : Gerriet M. Denkmann
DATE : Sat Jul 08 13:00:54 2006

On 08.07.2006, at 08:48, Ed Wynne wrote:

>
> On Jul 8, 2006, at 1:38 AM, Gerriet M. Denkmann wrote:

>> The problem: whenever (B) is initialized from (A) a random value 
>> in the range -0.5 ... +0.5 seconds is added to the time.
>> To test: make the time (B) equal to the correct wall clock time. 
>> Sleep. Awake. Compare time to wall clock. See difference of 
>> -0.5 ... +0.5 seconds.

>
> The hardware clock is probably only second accurate and its likely 
> the OS only samples it once, instead of polling for the next second 
> increment. This would save about .5s (on average) from the wakeup 
> time.


Yes; further proof for this is the fact that the system time after 
awakening always starts with a full second (no fractional part).

But: if the OS can poll the hardware clock, why can't I?

Gerriet.