My computer has been struggling with both internet performance and general responsiveness for over a year, including before I moved to my current apartment. The internet connection is rated at 500/500 Mbps, and my roommate consistently gets that speed, but my computer reaches only about 90/90 Mbps over Ethernet. I have tried multiple Ethernet cables, Wi-Fi, different network jacks, driver and motherboard updates, Windows updates, a virus scan, a system reset, and cleaning the computer. None of these made a meaningful difference.
The bigger issue is severe lag that gets worse the longer the computer is running. In online games such as Valorant and Dead by Daylight, my ping spikes, players freeze or teleport, audio cuts out, and the game eventually catches up. Discord can also become delayed, including camera footage arriving several seconds after the audio. My mouse sometimes moves unevenly across the desktop.
There are problems in offline software too. In the single-player game Blue Prince, everything starts normally but within a few minutes the game becomes smooth yet extremely slow, as though it is running in slow motion. The computer's fans have always been unusually loud compared with other PCs, almost like an airplane engine.
The system has an ASUS ROG STRIX B550-I GAMING motherboard, Ryzen 7 2700X processor, 32 GB of RAM, RTX 2080 Ti graphics card, and roughly 1.8 TB of storage. Reported CPU temperatures have looked fairly normal, generally around 30–50°C. What hardware or software tests should I run to determine whether this is a network adapter issue, thermal throttling, failing hardware, or something else?
4 Answers
The 100 Mbps ceiling could come from an intermediate switch or network device, especially if the wall outlet is wired through one. Ask whoever manages the apartment's network what equipment is between the outlet and router. Still, a defective network adapter can sometimes cause packet loss, so temporarily disabling the onboard Ethernet adapter and using a USB Wi-Fi or USB Ethernet adapter would be a useful test. If the lag continues while completely offline, the network hardware is not the root cause.
The consistent 90/90 Mbps result strongly suggests a 100 Mbps link somewhere, such as a damaged port, wall jack, switch, or adapter setting. Check the Ethernet adapter's link speed in Windows and make sure it is negotiating at 1.0 Gbps rather than 100 Mbps. Testing your PC on the exact cable and wall outlet your roommate uses is also useful. However, 90 Mbps is still more than enough for gaming, so it probably does not explain the freezing, audio dropouts, or offline slow-motion behavior. Those symptoms point to a separate PC problem.
The smooth-but-slow behavior in an offline game is especially important because it indicates this is not just latency or an internet provider issue. Check whether the GPU is overheating or losing power, whether the CPU is throttling, and whether the power supply is stable. Reseat the RAM and graphics card, test with one RAM stick at a time, and if possible try another known-good power supply or GPU. Before replacing parts, use a clean Windows installation from a USB installer rather than the built-in reset, since that rules out a damaged software installation more reliably.
I would stop focusing on internet speed and investigate hardware instability. The fact that games become worse after the system has been running, then improve after shutting down, along with loud fans and audio cutting out, could indicate thermal throttling or a failing component. Monitor CPU and GPU temperatures, clock speeds, usage, and fan speeds while the problem is happening—not just at idle. Also check SSD health, Windows Event Viewer, and run separate memory and CPU/GPU stress tests. A temperature monitoring tool may show the CPU or GPU dropping to very low clock speeds even when the reported temperature looks acceptable.
I tested the same jack and tried both Wi-Fi and several Ethernet cables, including a new one, without any improvement. The problem also existed before I moved, so I agree that the network connection probably is not the main cause.