Screen Artefacts: Coloured Lines, Squares and Flickering — Graphics Card, Driver or Monitor?

Artefacts are distortions of the picture that shouldn't be there: coloured lines, small squares, "snow", dots, flickering patches, stretched or "torn" textures in games. Sometimes they appear only under load, sometimes straight away at start-up, before Windows has even loaded. The causes vary widely: from a loosely plugged cable to failed video memory. Let's look at how to identify the source of the problem and what can be done.

What artefacts look like

• Horizontal or vertical coloured lines across the whole screen.
• A scattering of small coloured squares or dots.
• Distorted, "stretched" or flashing textures in games.
• Flickering in parts of the screen or the whole of it.
• Wrong colours, a "chessboard" pattern, a green or pink tint.
• The picture drops out and comes back, or the screen goes black for a second.

The first question: when do the artefacts appear?

Immediately at start-up, on the BIOS screen

If distortions are visible before Windows loads — on the manufacturer's logo or in the BIOS — the driver has nothing to do with it. It's almost certainly a hardware problem: the graphics card, video memory, cable or monitor.

Only in Windows

If start-up looks normal but artefacts appear in Windows, the problem is more likely the driver, settings or programs.

Only in games and under load

This is typical of overheating, an unstable overclock, a weak power supply or the beginnings of degradation in the graphics chip or memory.

Possible causes

The cable and connectors

A loose or damaged HDMI or DisplayPort cable, a cheap adapter or an oxidised connector often causes flickering, lines and the picture dropping out. It's the simplest and cheapest cause, and it's checked first.

The graphics driver

A damaged, unsuitable or conflicting driver causes distortions in Windows and games. A clean reinstall of the driver often solves the problem.

Overheating

A dust-clogged heatsink, dried-out thermal paste, worn thermal pads on the memory or a stopped fan lead to overheating, which brings artefacts and then crashes and shutdowns.

Overclocking

Overclocking the video memory or graphics processor is a common cause of artefacts. Sometimes the overclock is "factory", and over time the card can no longer sustain it.

The power supply

Unstable power under load can cause distortions and driver failures.

A faulty graphics card

Degradation of the graphics chip, failed video memory chips or damaged power components on the board. This is common with cards that have been mined on heavily or run hot for years.

The monitor or laptop screen

A faulty monitor or a laptop screen cable can look like graphics card artefacts. Connecting a different monitor or testing with another signal source helps tell them apart.

How to tell the graphics card from the monitor

A simple principle: if the artefacts remain when connected to a different monitor or TV, the problem is the graphics card or the computer. If the other monitor is clean but yours shows distortions with any source, the monitor is at fault. For a laptop, an external monitor is telling: if it's fine there, the screen or its cable is the likely problem.

Can the graphics card be saved?

If the cause is the driver, cable, overheating or overclocking — yes, and often inexpensively: cleaning, new thermal paste and pads, restoring factory clocks and the right driver. If the graphics chip has degraded or the memory has failed, repair requires specialised equipment, and the cost has to be weighed against the price of a new or used card. We give an honest assessment of whether a repair makes sense.

What not to do

Online you'll find advice to "bake" a graphics card in the oven or heat it with a heat gun. That isn't a repair: any effect is temporary, and the risk of destroying the card — or even getting burnt or starting a fire — is high. Nor should you keep gaming on an overheating card; it speeds up degradation.

How to extend a graphics card's life

Regular dust cleaning, good airflow in the case, a reasonable room temperature, a quality power supply and avoiding extreme overclocking all noticeably extend a graphics card's life. Every year or two it's worth checking temperatures under load — a rise is often the first sign that the cooling system needs servicing.

Keep an eye on fan noise as well. A card that has become much louder than it used to be is usually working harder to stay cool, and catching that early — before artefacts appear — keeps a simple cleaning job from turning into an expensive repair.

What our technician does

1. Establishes when the artefacts appear and checks the cables, connectors and monitor.
2. Performs a clean install of a suitable driver and resets any overclock.
3. Checks temperatures and stability under load.
4. Cleans the graphics card's cooling system and replaces thermal paste and pads.
5. Assesses whether a repair is worthwhile or selects a replacement card.

A real example

A gamer from Gldani came to us complaining that after half an hour of play flashing coloured triangles appeared, and then the driver crashed. Start-up and Windows looked clean. Our technician measured temperatures: the card's memory was reaching critical levels — the thermal pads had dried out and cracked over four years, and the heatsink was clogged with dust. After cleaning and replacing the thermal paste and pads, the memory temperature dropped by more than 25 degrees and the artefacts disappeared. The card carried on working without problems.

Call a technician

If artefacts have appeared on your screen, we'll come to any district of Tbilisi around the clock. Learn more on our computer diagnostics, PC cleaning and component upgrades pages.