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RE: RE: clock drift?


2.4.19 or later helps a lot. Then there is always the drift from the
oscillator supplying the input frequency to ETRAX. Not much you can do
about that. That drift is usally just a few ppms (can't remember the
maximum drift at the moment). External clocks such as the RTC on the
devboard usually has at least as much drift so that can't help you. 
I guess that there exist other hardware solutions with less drift.
To get close to zero drift you need an environment with controlled
temperature etc.


-----Original Message-----
From: owner-dev-etrax@xxxxxxx.com">mailto:owner-dev-etrax@xxxxxxx.com] On
Behalf Of Walter Harms
Sent: Friday, January 23, 2004 2:56 PM
To: dev-etrax
Subject: Re: RE: clock drift?

are there more informatin on clock drift and how to prevent it ?
The board here is exspected to run sometime without resync. Any
information would be helpfull.


- - - - - - - - - - - - - - Original Message - - - - - - - - - - - - - -
From: Mikael Starvik <mikael.starvik@xxxxxxx.com>
Subject: RE: clock drift?
Date: 01/23/04 14:35


There are a couple of issues with older kernels that causes clock drift:

1. Under high interrupt load some timer ticks could be lost. In some
rare cases this even caused the watchdog to bite. This was fixed
just after 2.4.14. Check in include/asm/irq.h if there is a 
BUILD_TIMER_IRQ macro. If not you have this problem.
2. The normal timers in ETRAX runs 64ppm too fast. This has been
fixed after 2.4.16.


-----Original Message-----
From: owner-dev-etrax@xxxxxxx.com">mailto:owner-dev-etrax@xxxxxxx.com] On
Behalf Of Ronny L Nilsson
Sent: Friday, January 23, 2004 2:27 PM
To: dev-etrax
Subject: clock drift?

I'm woundering if anyone but me has experienced substantial system 
clock drift with devboard_lx? I've had reports of the system time being 
several hours off after just a couple of days uptime. Some drift I 
expect since I'm not using NTP but several hours? Anyone has an idea?


P.S. Kernel 2.4.14 used.