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Date: Fri, 19 May 2006 10:08:26 +0200
From: Steven Scholz <steven.scholz@imc-berlin.de>
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To: linuxppc-embedded@ozlabs.org
Subject: Re: MPC8xx: resolution of gettimeofday() ?
References: <446C8E70.3040601@imc-berlin.de>
	<20060518164812.GA21075@gate.ebshome.net>
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Eugene,

>> what is the resolution of gettimeofday() for an MPC8xx?
>>
>> IIUC then the "decrementer" is used to generate the timer interrupts every 10ms.
>>
>> This decrementer runs at cpuclk/16. Thus with 80MHz CPU clock has a
>> resolution of 16/80MHz = 200ns and overflows every 50000 ticks.
>>
>> But is this decrementer used to update xtime?
>> Will gettimeofday() have a resolution of 200ns?
>>
>> How about linux 2.4 where xtime is a "struct timeval" rather then "struct
>> timespec"?
>>
> 
> Usually on PPC we use timebase to interpolate time between Decrementer 
> interrupts. In this case gettimeofday resolution is determined by 
> timebase resolution which is quite high (megahertz range).

Sorry. I don't understand. What do you mean with "timebase"? Is there a
second timer/counter?

-- 
Steven