[ale] UTC time vs GPS time, not the same???

[Ron Frazier]

Hi guys,

I've been doing some additional research on computer time keeping and 
such.  I just read that GPS time does not account for leap seconds (the 
seconds periodically added to match UTC time with astronomical time).  
The statement also said that because of this, there is about a 15 second 
difference between GPS time and UTC time, even though the clocks are 
highly accurate.  Does anyone know if this is true?  If so, a GPS clock 
might not be the best source for time on a computer network, especially 
if computers being communicated to are being synced to UTC.

I'd also REALLY like to know why the clocks in computers are so widely 
variable.  I know the software clock in the OS is synced to the hardware 
clock at boot.  But, after that, it apparently varies widely in 
performance, even though it's receiving periodic interrupts from the 
hardware clock.  Is it really the case that some routines switch off the 
hardware interrupts, causing the software clock to miss cycles?  If 
that's true, why are user level programs allowed to do that.  You'd 
think processing the hardware interrupt from the hardware clock would be 
a pretty important thing.

Thanks in advance for any info you share.

Sincerely,

Ron

-- 

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Ron Frazier

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