NTP and hardware clocking


Hello there,

I’m making some tests and i have a question: how the ntp synchronization process affect the hardware clocking, for example: How the CPU clock PLL is affected by NTP corrections with a PPS input? Have any correlation or all ntp process only “discipline” and correct the system (kernel side) timer i think CPU and another peripherals PLLs are distinguish things…

Best regards, this forum is awesome!

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NTPD only affects time via the kernel / software timer. It tries to characterize how fast / slow the RTC is in relation to the time it gets from whatever sources you choose (PPS or other NTP servers).

I know Chrony can update the RTC time periodically, I don’t know about NTPD. I believe when you reboot in linux though it syncs the clocks too.

There is no hardware adjustment in PCs. It’s just a cheap crystal oscillator (not even temperature compensated) and a clock gen chip to create the various frequencies necessary for various parts of the board.

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Alright so, if we want to discipline internal hardwares pll we should have a external oscillator that can handle this control and… This will not affect by ntp time ?