[ntp:questions] 500ppm - is it too small?

Richard B. Gilbert rgilbert88 at comcast.net
Thu May 7 17:20:36 UTC 2009


David J Taylor wrote:
> Richard B. Gilbert wrote:
> []
>> An error greater than 500 PPM suggests seriously broken hardware! 
>> There might be some way to "kludge" the software to compensate for
>> this brokenness but I think it would be easier and cheaper to fix or
>> replace the broken hardware.
> 
> I was trying to see what errors might be expected in the typical PC 
> clock crystals, but my gut instinct is to agree with you.  However, 
> suggesting that someone replace their pride and joy just because it 
> doesn't run ntp is unlikely to elicit a favourable response!

I'm not here to make people feel good!

I've checked the hardware available to me and none is worse than 50 PPM.
That's two PC's running Windows XP, three Sun Ultra 10 Workstations 
running Solaris 8, 9, and 10, two DEC Alpha workstations running VMS.

The specifications for NTPD say that it will correct errors less than or 
equal to 500 PPM.

I beleive that hardware outside of this limit can properly be described 
as broken!  Would *you* tolerate a clock, computer or wall, that gained 
or lost more then 43 seconds per day?  Our forefathers, limited to 
springs, gears and pendulums could do better than that.




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