At Nvidia, RSUs are subject to a 4-year vesting schedule: 25% vests at the end of the 1st year (cliff), then 25% in each of the 2nd, 3rd and 4th years (6.25% every 3 months).
Nvidia commonly refers to RSU as NSU (Nvidia Stock Unit). Although the name is different, it is the same as RSU's. Vesting dates throughout the year are standardized regardless of start date. Vesting occurs third Wednesdays in March, June and September, and on the second Wednesday in December.