And so does my Fedora install (let's not blame Redmond unnecessarily).
My Android phone is even worse - it drifts by about 5-10s a day. Not a nightmare but it's still a lot more than my (probably unrealistic) expectations of 21st century hardware.
My Android phone is even worse - it drifts by about 5-10s a day. Not a nightmare but it's still a lot more than my (probably unrealistic) expectations of 21st century hardware.
It isn't particularly an OS probably at all at the root: it is a hardware problem. The RTCs in PC have historically not been terribly reliable so OSes tend to ignore them where at all possible.
The probably here is probably the same as seen inside VMs: the OS is trying to count timer interrupts and other such references to gauge the passage of time, but with CPUs changing their speeds constantly this in itself becomes difficult to make accurate.
Windows' default behaviour of occasionally checking an external time reference (IIRC it checks approximately three times per day if your machine is on 24 hours) is often inadequate IMO though. Much better would be to use proper (relatively constant) NTP checking and clock skewing, though that imposes an extra infrastructure load.
Apparently clocks are hard.
You can still run hwclock on your Fedora box and get genuine RTC readout if you need it.
The really old way of timekeeping was to basically advance the system time by a constant amount, in an interrupt routine which might have been triggered by the ancient timer chip, and interpolation done between those ticks using the cpu TSCs.
And actually hwclock accesses /dev/rtc* which is just an arbitrary character devices (which the kernel indeed can use to initialize its notion of time on boot up), it's never accessed with the standard syscalls gettimeofday() or clock_gettime().
So while I really like MS bashing from time to time, in this case it's probably not too negligent of them, there might even be a standard way of informing the OS kernel about a change in TSC speed?