Possibly not of immediate concern to time-nuts but an article had some trigger words for them in the initial fixes to the much publicised problems with Intel/AMD/ARM etc : "After these changes, the time stamp returned by |performance.now| will be less precise due to lower resolution. Some browsers are going a step further and degrade the accuracy by adding a random jitter." https://hackaday.com/2018/01/06/lowering-javascript-timer-resolution-thwarts-meltdown-and-spectre/ meltdown/spectre background https://www.theregister.co.uk/2018/01/04/intel_amd_arm_cpu_vulnerability/

From: David Possibly not of immediate concern to time-nuts but an article had some trigger words for them in the initial fixes to the much publicised problems with Intel/AMD/ARM etc : "After these changes, the time stamp returned by |performance.now| will be less precise due to lower resolution. Some browsers are going a step further and degrade the accuracy by adding a random jitter." https://hackaday.com/2018/01/06/lowering-javascript-timer-resolution-thwarts-meltdown-and-spectre/ meltdown/spectre background https://www.theregister.co.uk/2018/01/04/intel_amd_arm_cpu_vulnerability/ ================================ David, This API appears only to affect browsers. On my Windows systems most have been patched, and I see no visible difference on either PPS-synced, LAN-synched or Wi-Fi devices as recorded by NTP. One PC showed an increase in CPU usage, but other PCs performing similar tasks have not. That same PC showed a doubling of jitter from less than 2 microseconds to less than 4 microseconds. It's an i5-4460 Haswell processor. http://www.satsignal.eu/mrtg/harstad-cpu-week.png Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-taylor@blueyonder.co.uk Twitter: @gm8arv

These bugs is a big deal. I even had to answer customer questions on them. Interesting how you can use the cycle counter to deduct information out of that channel, forming a side-channel. Adding random jitter only slows down the attack, as the average bias difference won't change. Cheers, Magnus On 01/07/2018 03:53 PM, David J Taylor via time-nuts wrote: > From: David > > Possibly not of immediate concern to time-nuts but an article had some > trigger words for them in the initial fixes to the much publicised > problems with Intel/AMD/ARM etc : > > "After these changes, the time stamp returned by |performance.now| will > be less precise due to lower resolution. Some browsers are going a step > further and degrade the accuracy by adding a random jitter." > > https://hackaday.com/2018/01/06/lowering-javascript-timer-resolution-thwarts-meltdown-and-spectre/ > > > meltdown/spectre background > https://www.theregister.co.uk/2018/01/04/intel_amd_arm_cpu_vulnerability/ > ================================ > > David, > > This API appears only to affect browsers. > > On my Windows systems most have been patched, and I see no visible > difference on either PPS-synced, LAN-synched or Wi-Fi devices as > recorded by NTP.  One PC showed an increase in CPU usage, but other PCs > performing similar tasks have not.  That same PC showed a doubling of > jitter from less than 2 microseconds to less than 4 microseconds.  It's > an i5-4460 Haswell processor. > >  http://www.satsignal.eu/mrtg/harstad-cpu-week.png > > Cheers, > David