Every few weeks a gaming PC comes through the EH11 workshop from Tranent, Prestonpans or Cockenzie with the same brief written on the job sheet: “wired to the router, still laggy, Wi-Fi has been ruled out”. The customer has already done the sensible thing and dropped a cable from their desk to the router, which is why the message is more frustrated than usual. Wi-Fi is the easy villain. When the cable is in and the lag spikes still arrive on cue, people assume it has to be the computer.
In fairness, it sometimes is. More often it is one of a handful of boring causes that look identical from the player’s side — a ping graph that walks along at 18 ms for ninety seconds and then spikes to 280 ms for a round, then settles again. These notes are the way we actually work through those jobs on the bench at Parkhead Drive, in roughly the order the faults turn up, so you can tell before you unplug the tower whether it is worth bringing in or whether a ten-minute change at the desk will fix it.
The Classic Tranent Bench Scenario
A lot of the East Lothian houses we visit on home callouts have the master socket in the hallway and the router near the front door, with the gaming PC a floor above or at the back of the house. The run to the desk is usually a long thin cable that was already in the drawer, stapled to the skirting, folded under a rug, or threaded along a cable tray that also carries mains flex. That cable almost always says Cat 5e or Cat 6 on the sheath, and it almost always tests fine for a plain web browser. It is only under load, with a game sending small packets back and the Windows Update service trying to pull a feature update down in the background, that the problem shows up as a ping spike.
Before anything else we want to know two numbers: the ping to the local router (type ping 192.168.1.1 -t in a Command Prompt and leave it running), and the ping to a server outside the house, usually ping 1.1.1.1 -t. If the first one spikes along with the game, the fault is inside the house. If the first one is a steady 1 ms the whole evening and only the second one spikes, the fault is upstream of the router. That one split tells us whether we are opening the tower, swapping a cable, or ringing the ISP.
Ethernet Is Not Automatically Low Ping
The folklore that a cable is always faster than Wi-Fi is only half right. A cable removes the airtime contention, the channel interference and the roaming between access points, but it does not magically produce low latency on its own. If the Network and Sharing Center shows the connection running at 100 Mbps rather than 1 Gbps, you are already on a degraded link — one of the four twisted pairs in the cable has failed, or the port at either end is older than the cable, and the PC has fallen back to the ancient 100BASE-TX standard. That link is enough for the game itself, but the moment anything else on the PC pulls bandwidth, the queue fills and your ping grows while the queue drains.
On the bench we check the link speed first because it is instant. In Windows, settings → network & internet → Ethernet, scroll down to the properties for the adapter, and look for “Link speed (Receive/Transmit)”. If that number is 100/100 instead of 1000/1000, the cable or a port is the suspect before anything else is touched.
The Cable Itself Is the First Suspect
Cheap patch leads from loose multi-packs are a running source of trouble. The copper is sometimes copper-clad aluminium rather than solid copper, which looks the same but is far more fragile at the plug and more susceptible to interference under load. Cables that have been pinched by a door, kinked around a sharp skirting edge, or run alongside mains flex for a few metres will show up as a working-but-flaky link that gets worse as the house warms up in the evening. We keep known-good flat Cat 6 cables on the shelf exactly for this swap-and-see test. If a fresh cable turns an evening of spikes into a flat line, the old one goes in the recycling bin and we are done.
Length matters less than people fear, but termination matters a lot. A plug crimped at home with a cheap tool is usually the worst joint in a run — the pairs are untwisted too far before the connector, which lets crosstalk in. If a run passes through a wall socket, every faceplate is another two joints to check. Where a long permanent run has to stay in place, we test it with a proper cable qualifier rather than a continuity beeper, because a cable that passes continuity can still be well out of spec for 1000BASE-T.
Switches, Powerline and the Hidden Hops
Half the gaming PCs we see from Prestonpans and Cockenzie are not actually plugged into the router at all. They are plugged into a small five-port switch under the desk, which in turn goes to a powerline adapter, which in turn goes to the router down in the hallway. Each hop adds a small amount of latency on a good day and a lot of latency on a bad day. Powerline in particular behaves well on a quiet circuit and badly as soon as a washing machine, an induction hob or a fridge compressor cycles in the kitchen. The spikes line up with the washing machine; the customer never puts the two together.
If there is a powerline link anywhere in the chain, the quickest test is a long temporary cable laid along the floor from the gaming PC straight to the router for the evening. If the ping flattens out, the powerline is the cause and the right fix is either a proper Ethernet run or a decent mesh with a wired backhaul — our note on powerline vs mesh in Linlithgow covers the trade-off in detail. If a cheap unmanaged switch is in the chain, we check it is actually a gigabit model and not a 100 Mbps one from the back of the drawer; the box labelling is not always honest.
Drivers, Offload Settings and Windows Updates
When the cable, the switch and the link speed all check out, the next suspect is the PC itself. The Realtek and Intel network drivers that ship inside Windows are usually fine for browsing but have one setting called interrupt moderation, and on some adapters it defaults to high. Interrupt moderation groups incoming packets together to save CPU time, which is sensible for a file server and terrible for a competitive game. In Device Manager, right-click the Ethernet adapter → properties → advanced, and look for “Interrupt Moderation” or “Interrupt Throttle Rate”. On a gaming PC we set it to Off or Low and the spikes often go away.
A fresh driver straight from the Realtek or Intel website — not the one Windows Update picked — also catches a surprising amount, especially after a recent feature update. If the PC has had hands laid on it recently for something unrelated, our OS installation service covers a clean driver pass as part of a tidy-up. On a brand-new build where the fault is on day one, that is almost always a BIOS or chipset-driver problem rather than a cable one, and we check that under our custom PC build work.
Background Apps That Steal Bandwidth
The single most common cause of “wired but still laggy” we see is nothing wrong with the network at all. It is OneDrive syncing a photo folder, Steam downloading a 70 GB update in the background, a Windows feature update, or an Xbox app pre-loading the next game in the series. Each of those will happily use the full line, and most domestic routers do not know how to prioritise the small gaming packets against them. The ping to the router stays low, the ping to the game servers climbs with the queue, and the player gets blamed for “their internet”.
Resource Monitor, under the Network tab, is the quickest way to see which process is actually sending at the moment the spike happens. If a svchost.exe is pulling at 60 Mbps, that is Windows Update; it can be told to defer with the active-hours setting. If a background Steam download is the culprit, Steam has a bandwidth limiter and a schedule in its settings. If the system looks clean but the uplink is still saturated, it is sometimes the first sign of a quietly misbehaving browser extension or outright malware, which falls under our virus and malware removal service.
When the Fault Is Actually at the ISP
If the ping to the router is a flat 1 ms all evening and only the ping to 1.1.1.1 spikes, the house wiring and the PC are off the hook. In Tranent and the surrounding East Lothian estates, the mix of Openreach fibre-to-the-cabinet, fibre-to-the-premises and the older cable network means the right next step depends on which service you are on. A short-term drop that happens at exactly the same time every evening is almost always ISP congestion at the local cabinet; a random lag spike that lasts seconds is more likely a line fault that your provider’s own diagnostics will not pick up on their own. We cover the differences in why a fibre upgrade did not speed up the Wi-Fi, and the same logic applies to wired connections.
If several devices in the house are affected at the same time and the pattern repeats, it is worth logging a fault with your provider — a BT Wholesale line test only picks up the obvious cases, but running it is still the quickest way to escalate. If only the gaming PC is affected and other machines on the same cable are fine, the fault is on the PC side and we are back to the earlier sections.
What To Try Before You Bring the PC In
Before you unplug the tower, do these five things in order: open a Command Prompt and leave ping 192.168.1.1 -t running in one window and ping 1.1.1.1 -t in another; check the link speed in network settings and confirm it says 1000; swap the Ethernet cable for a different known-good one, with no powerline or spare switch in the middle; open Resource Monitor and watch which process is using the uplink at the moment the ping spikes; and look in Device Manager for Interrupt Moderation on the Ethernet adapter. Nine times out of ten, one of those five tells us where the fault is before the PC leaves the desk.
If it still spikes after all of that, the problem is worth bringing in. Our Tranent gaming PC repair page has the collection and turnaround detail for East Lothian postcodes, and the deeper network-side work — replacing a dodgy integrated NIC with a known-good PCIe card, tracing a crosstalk fault in a house run, or configuring a router’s QoS to prioritise the games port — sits under our networking and Wi-Fi service. Related reading if the lag follows a different pattern: gaming PC dropping Wi-Fi mid-match in Bathgate if the connection drops rather than spikes, and one PC in Cockenzie saying connected but no internet if only your machine is affected.
Last updated: 28 October 2026