I am currently using i3-13100 with 32gb or ram and samsugn pro 980 2tb on a headless arch 6.12.39-1-lts I found a solution, turned out there was a file in Linux sysfs filesystem where ASPM was disabled. Enabling the l1_aspm file let me reach C10 states, but it did bring down download speed notably. Although enabling both l1_1_aspm l1_2_aspm and clkpm wasn't necessary, they did come with a higher performance cost. Interestingly, upload speed stayed the same at 45 Mbit/s despite any changes made. PS: Just after writing this message, I found out that the solution to enable ASPM had already been shared, but I must've missed it.