The short version
A graphics card is a second computer built for one job: drawing millions of pixels, many times a second. A 4K screen has 8.3 million pixels, and at 60 fps the card has to work out about 500 million pixel colors every second, each needing many calculations. Its main chip, the GPU, does that with thousands of small cores working at once.
- GPU chipHow many cores it has and how fast they run decides the frame rate.
- VRAMThe card's own fast memory for textures and the frame being drawn. Run out and performance falls off a cliff.
- TricksUpscaling (DLSS, FSR) and frame generation draw fewer pixels and fill in the rest.
Why thousands of small cores?
Made-up numbers to show the ideaA CPU has a few big, clever cores that are great at long chains of steps that depend on each other. Coloring pixels is the opposite: millions of small jobs that don't depend on each other at all. So a GPU trades clever for numerous. The RTX 5090 has 21,760 cores; an RX 9070 XT has 4,096.
How a frame gets drawn
Simplified: a real frame has millions of trianglesEverything in a 3D game is built from triangles. Every frame, the graphics card runs the same assembly line to turn those triangles into the image on your screen.
- Ray tracing adds another step: tracing the path of light rays as they bounce around the scene, for realistic reflections, shadows and lighting. It's very demanding, and modern cards have dedicated ray tracing cores to speed it up. NVIDIA's are currently the strongest.
- The CPU sets the pace too. The CPU has to prepare every frame's draw calls. At 1080p a fast graphics card can finish its part sooner than the CPU can feed it, which is why CPU choice matters most at high frame rates (see How CPUs work).
Resolution, frame rate and VRAM
Real benchmark results for every card we trackMore pixels means more work for every frame, so frame rates drop as resolution rises. Pick a card to see how much.
- VRAM holds the textures, models and frames the GPU is working on. It's much faster than your PC's RAM, and sits right next to the GPU on the card.
- When a game needs more VRAM than the card has, data has to come across from system RAM, which is far slower. The table above shows it: the 8GB versions of the same chip keep up at 1080p but fall well behind at 4K, where textures and frames take more space.
- Memory bus width (128-bit, 256-bit and so on) is how many bits move between the GPU and its VRAM each transfer. Wider buses feed faster chips, which is why high-end cards have them.
Upscaling and frame generation
Render resolutions are the standard DLSS / FSR scale factorsUpscalers like NVIDIA's DLSS, AMD's FSR and Intel's XeSS render each frame at a lower resolution, then use AI to rebuild it at full resolution. In Performance mode at 4K, the card only draws a quarter of the pixels. Frame generation goes further, inventing whole frames between the real ones.
Power and heat
All those cores use a lot of power. Graphics cards are usually the biggest power user in a gaming PC, from around 130 W for an RTX 5050 to 575 W for an RTX 5090. That's why big cards have huge coolers and need a strong power supply (try the power supply calculator) and a case with room and airflow (see the PC case guide).
What this means when you buy
- Buy for your monitor. The resolution and refresh rate you play at decide how much card you need. The Which graphics card? guide shows today's cheapest card for 60 and 100+ fps at each resolution.
- Don't skimp on VRAM for 1440p or 4K, or if you keep cards for years: 12–16GB is the comfortable range.
- Upscaling is a free speed boost worth using, especially at 4K. Frame generation makes motion smoother, but it doesn't make a slow card feel fast.
- Brands matter less than the chip. An RTX 5070 from any maker performs within a few percent of another; pricier models mostly add quieter coolers and looks.
Today: RTX 5070 from …, RX 9070 XT from …, RTX 5060 Ti 16GB from ….