Mister_hass
Newbie level 5
Hi all,
Jitter used to be a topic of high importance in CPUs in the 90ies and 2000, then it became silenced for the last 10 years.
Today's 2.5GHz PLLs jitter is less than 1ps-RMS correspondiing to 15 sigma of 15ps. Surprisingly people still close timings in CPU design using up to 80ps margin. Knowing that skews are less than 10ps, then why up to 70 ps is still allocated to jitter tolerance margin?
Can anyone confirm these numbers and why they are still in use.
Many thanks
Jitter used to be a topic of high importance in CPUs in the 90ies and 2000, then it became silenced for the last 10 years.
Today's 2.5GHz PLLs jitter is less than 1ps-RMS correspondiing to 15 sigma of 15ps. Surprisingly people still close timings in CPU design using up to 80ps margin. Knowing that skews are less than 10ps, then why up to 70 ps is still allocated to jitter tolerance margin?
Can anyone confirm these numbers and why they are still in use.
Many thanks