Mauricio ha scritto:
POSIX realtime extensions have been developed to be high reliable.
(...) However, they offer
no guarantees on interval measurements, and the correction algorithms
can cause the measurement of a time interval of an hour or so duration
to be off by +/- 1 sec, especially within the first few hours after a
cold boot. (...)
At the start of this thread, my assumption was that
all computers had a 100% reliable tick counter.
High Precision Event Timer (http://en.wikipedia.org/wiki/HPET) should be
pretty reliable, but it will never be as reliable as a dedicated clock.
Well,
this shows I understand nothing about hardware.
My problem is that the equipment I interact with is
supposed to deliver data at a constant rate.
What is the rate value?
How do you read the data?
Since
I don't know how much its engineers care about
patients, I wanted to be sure not to save wrong
information.
You should trust the engineers, IMHO, since that is a medical equipment
and should be more reliable than a PC.
Read carefully the equipment specification.
It wouldn't matter if the clock is
saying we are on XVII century, as long as 10 seconds
would never be 10.1.
But, as I learned from you, my PC is not to be
considered as a reference. Maybe the right approach
is to ask people who understand hardware if mine is
actually a valid concern.
If you can, you should ask to the equipment producer.
If you are on a POSIX system, store both the time information from the
equiment and from clock_gettime(CLOCK_MONOTONIC), but only trust the
equipment.
Thanks,
Maurício
Regards Manlio
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