Hi there, I did some testing, and it turns out the sample solution doesn't unblock if the unblock time occurs while another process is unblocking. I think that in the sample solution, it only checks through once if anything can be unblocked when the CPU is idle and doesn't account for the time elapsed during the context changes. When a process unblocked 10usecs elapses. During that time, another blocked process may unblock. In the screenshot below, the sleeping function is meant to unblock at time 89, but instead only unblocks after the previously unblocked process has finished using the CPU.