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Many computer systems measure time and date using Unix time, an international standard for digital timekeeping.Unix time is defined as the number of seconds elapsed since 00:00:00 UTC on 1 January 1970 (an arbitrarily chosen time based on the creation of the first Unix system), which has been dubbed the Unix epoch.
Computer clocks of the era were not sufficiently precisely set to form a precedent one way or the other. The POSIX committee was swayed by arguments against complexity in the library functions, [ citation needed ] and firmly defined the Unix time in a simple manner in terms of the elements of UTC time.
System time is measured by a system clock, which is typically implemented as a simple count of the number of ticks that have transpired since some arbitrary starting date, called the epoch. For example, Unix and POSIX -compliant systems encode system time (" Unix time ") as the number of seconds elapsed since the start of the Unix epoch at 1 ...
Constant TSC behavior ensures that the duration of each clock tick is uniform and makes it possible to use the TSC as a wall-clock timer even if the processor core changes frequency. This is the architectural behavior for all later Intel processors. AMD processors up to the K8 core always incremented the time-stamp counter every clock cycle. [6]
Software timekeeping systems vary widely in the resolution of time measurement; some systems may use time units as large as a day, while others may use nanoseconds.For example, for an epoch date of midnight UTC (00:00) on 1 January 1900, and a time unit of a second, the time of the midnight (24:00) between 1 January 1900 and 2 January 1900 is represented by the number 86400, the number of ...
The Linux kernel can also use HPET as its clock source. The documentation of Red Hat MRG version 2 states that TSC is the preferred clock source due to its much lower overhead, but it uses HPET as a fallback. A benchmark in that environment for 10 million event counts found that TSC took about 0.6 seconds, HPET took slightly over 12 seconds ...
syn1588 PTP Stack from Oregano Systems: A portable implementation of the complete IEEE1588-2008 standard with special features like Boundary Clock support, Unicast operation, IPv6 support and security enhancements. [93] The Linux PTP Project – an implementation of the Precision Time Protocol (PTP) according to IEEE standard 1588 for Linux ...
Jiffy values for various Linux versions and platforms have typically varied between about 1 ms and 10 ms, with 10 ms (1/100 s) reported as an increasingly common standard in the Jargon File. [ 11 ] Stratus VOS (Virtual Operating System) uses a jiffy of 1/65,536 second to express date and time (number of jiffies elapsed since 1 January 1980 00: ...