[time-nuts] M$-Vi$ta-compliant PC RTC clock card?

Hal Murray hmurray at megapathdsl.net
Thu Sep 20 13:54:51 EDT 2007

> One factor to remember about good ol' PCs is that not all of the
> timing problem is down to the RTC. A lot of timing errors are down to
> Interrupts. A busy PC can lose 100s of milliseconds a day as a result
> of Interrupt activity.

Lost  interrupts are usually a sign of poor setup/configuration or buggy 

Ages ago, when I first setup this Linux system, the kernel default was DMA 
off for the disk driver.  It was easy to generate lost interrupts with enough 
disk activity.  One tweak in the right place fixed that.

> Personally I don't worry about the base accuracy of the PC (RTC or
> other), and make sure I'm running NTP linked to a good reference
> source. 

I'd expect ntp to have serious troubles with lost interrupts.  How often does 
your clock get stepped?

I guess it might work well enough if all you want is to be within a few 
seconds so time stamps on files and mail are reasonably close.

These are my opinions, not necessarily my employer's.  I hate spam.

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