RHEL7: Clock is not accurate on Intel Xeon SP systems, and time sync fails

Solution Verified - Updated -


  • System clock is not accurate
  • System clock is getting faster or slower
  • ntp time sync fails in slew mode
  • tsc clocksource calibration fails
  • Absence of the following message in kernel log: tsc: Refined TSC clocksource calibration:


  • Red Hat Enterprise Linux 7
  • Red Hat Virtualization Host 4
  • Intel Skylake architecture based CPUs (Scalable families such as Cascade Lake)
  • Bare metal machine (we did not get any reports from RHEV/RHV guest VMs)

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