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Re: [ts-7000] LInux 2.6: Why is EP93XX_TIMER1_LOAD set to 508469

To: "" <>
Subject: Re: [ts-7000] LInux 2.6: Why is EP93XX_TIMER1_LOAD set to 508469
From: Per Öberg <>
Date: Tue, 9 Mar 2010 10:49:15 +0100

> > well, it's not exactly 508 kHz as the docs claims, but it's 14.7456 Mhz
> > divided by 29 = 508496. The timer is 16-bit only, you can't feed it with
> > this value anyway.

Yeah, I noticed... =) 

It's one of those things that you should list as the first things to check
when the results aren't as expected. (As well as not using N as the last index
to a N-size array...)

> Actually I found 5084 gives a better system clock. Using adjtimex and some
> clockwatching allows one to have a system clock with an accuracy of about
> 2ppm (assuming a fairly constant environment). That's about 1 sec drift in
> 5 days.

While on the subject... It looks like in the code that Timer 4 is actually
used to compensate for the driftoff somehow. If not, what is the purpose of
counting "lost jiffies" as the comment says?

Thanks
Per Öberg


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