Computer Architecture & Hardware Maintenance lectures full playlist :

https://youtube.com/playlist?list=PLBV6VAQlom0k6FhyVNFO_QLiPgu-eWOod

Introduction to CPU -
https://youtu.be/WBiZFWA3_ew

General Register Organization -
https://youtu.be/W8HojQhCxXI

Stack Organization Part 1
https://youtu.be/m8DpJBI-6Tg