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Date: Wed, 28 Feb 2001 23:37:40 +0000
From: "Andrew Morton" <morton@nortelnetworks.com>
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To: ebuddington@wesleyan.edu
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Subject: Re: time drift and fb comsole activity
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Eric Buddington wrote:
> 
> I know this has been reported on the list recently, but I think I can
> provide better detail. I'm running 2.4.2 with atyfb on a K6-2/266
> running at 250. This system has no history of clock problems.
> 
> adjtimex-1.12 --compare gives me "2nd diff" readings of -0.01 in quiescent
> conditions.
> 
> flipping consoles rapidly cboosts this number to -3 or -4.
> 
> catting the full documentation to ntpd (seemed appropriate) gives me
> "2nd diff" numbers a little over 34. If I read the numbers correctly,
> 47 seconds of CMOS time passed while the system clock only passed 13
> seconds.
> 
> The processor and the CMOS clock were moving at zero velocity relative
> to each other, and were both in normal Earth gravity.

The kernel blocks interrupts during console output.  fbdev
consoles are slow.  Net result: many lost timer interrupts.

I'm working on it.  Slowly.  Should have something next week.

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