Re: Hardware Clock
Re: Hardware Clock
- Subject: Re: Hardware Clock
- From: "Gerriet M. Denkmann" <email@hidden>
- Date: Sat, 8 Jul 2006 07:38:44 +0200
On 08.07.2006, at 00:21, Shawn Erickson wrote:
On 7/7/06, Gerriet M. Denkmann <email@hidden> wrote:
How can I read the hardware clock?
(Not the system clock as in NSDate or gettimeofday, but the thing
which keeps the time when the computer is sleeping or turned off).
Maybe some Carbon function? Or Unix call? IOKit?
Not sure I understand the question... can you better explain what you
are trying to do?
(A) Well, to my understanding, there is some hardware hidden in my
computer which keeps the time when the computer is switched off.
(B) On the other hand, when the computer is running, the CPU keeps
the time, which then can be accessed via gettimeofday() or NSDate.
This latter time (B) is initialized from (A) at start or at awakening
from sleep.
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.
What I want to achieve:
1. a better understanding of what is going on.
2. reading the time (A)
3. try to eliminate this random change of time after each awakening.
Gerriet.
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