have an acer aspire 3 with the same cpu. When on linux kernel 5.4, it throttles to about 800MHz and further down after playing for ~55 minutes, gpu clock throttles as well. On subsequent kernel versions i experience even harsher throttles, same as described here, IMMEDIATELY after switching to a game window.
5.4: this doesn't seem to be a thermal throttle issue, as i kept the temperature under 45C for tests. then, i ran some cpu stressing and it seems to be working fine if gpu isn't used. it's really weird that the throttling starts after a fixed amount of time, i have no idea what to do
