Fundamentals · Updated in 2026
Thunderbolt, USB-C, DisplayPort, HDMI: the guide that avoids nasty surprises
Most disappointments on first switch-on come from a port or a cable, never from the monitor. Here is what each standard actually carries, how much bandwidth your monitor demands, and how to check in thirty seconds that your machine will keep up.
USB-C is not a video standard
This is the most costly confusion. USB-C describes the shape of the connector, nothing more. A USB-C port can carry data alone, data and charging, or video as well — and nothing tells them apart to the eye.
What makes video possible is called DisplayPort Alt mode. To find out whether your port has it, look for the small DisplayPort logo (a stylised D) or the Thunderbolt lightning bolt next to the socket. A Thunderbolt 3, 4 or 5 port always carries video. On many laptops, only one USB-C port in two or three can drive a display.
Thunderbolt: the USB-C that does everything
Thunderbolt uses the USB-C connector but guarantees video, fast data and charging. Thunderbolt 3 and 4 reach 40 Gb/s; Thunderbolt 5, which has appeared on recent machines, reaches 120 Gb/s. On an Apple Silicon Mac, every port is Thunderbolt: the question does not arise.
DisplayPort: the fastest route on a desktop
- DisplayPort 1.4 — 32.4 Gbit/s raw, about 25 usable. Ample for 5K at 60 Hz, and for 6K thanks to DSC compression.
- DisplayPort 2.1 UHBR20 — up to 80 Gbit/s. That is what lets the P27Z display native 5K at 180 Hz, and the G32P and G32X drive their 6K panel.
- DSC compression — visually lossless, handled by the graphics card. All NVIDIA GeForce RTX and AMD Radeon RX 6000 and later support it. Without DSC, an older card tops out at 4K.
HDMI: mind the version
This is the most common trap, because the connector is identical in both cases.
- HDMI 2.0 — 18 Gbit/s. Enough to display 4K at 60 Hz, no more. The Kuycon Q34W and P40K have it: on those two models, the full refresh rate goes strictly over DisplayPort or USB-C.
- HDMI 2.1 — 48 Gbit/s. 4K at 144 Hz, 5K at 60 Hz, and the 120 Hz modes of recent consoles. That is what the G27P, P27D, P32K, P32T, G32P and G32X have.
Reference
How much bandwidth for what
| Target display | Bandwidthapproximate | What is enough | Models concerned |
|---|---|---|---|
| 4K at 60 Hz | ~12.5 Gbit/s | HDMI 2.0, DP 1.4, USB-C | P27L, P40U |
| 4K at 144–160 Hz | ~30 Gbit/s | HDMI 2.1 or DP 1.4 + DSC | P27D, P32K, P32T |
| 4K at 240 Hz | ~50 Gbit/s | DP 1.4 + DSC or better | Q32S |
| 3440 × 1440 at 165 Hz | ~26 Gbit/s | DP 1.4 (not HDMI 2.0) | Q34W |
| 5120 × 2160 at 120 Hz | ~35 Gbit/s | DP 1.4 + DSC | P40K |
| 5K at 60 Hz | ~17 Gbit/s | DP 1.4, HDMI 2.1, Thunderbolt | G27P, G27X SE |
| 5K at 180 Hz | > 50 Gbit/s | DP 2.1 UHBR20 | P27Z |
| 6K at 60 Hz | ~26 Gbit/s | DP 2.1, HDMI 2.1, or DP 1.4 + DSC | G32P, G32X |
Indicative values at 10-bit, before compression. DSC greatly reduces the real requirement.
Charging over the video cable
A USB-C monitor powers the laptop over the same cable as the picture: that is Power Delivery. The Kuycon models concerned deliver up to 100 W, which covers a MacBook Air, a 14-inch MacBook Pro and almost every Windows laptop. On a machine whose original charger exceeds that power — a 16-inch MacBook Pro, for example — charging simply happens more slowly under a full workload.
Cables, adapters and docks
- Use the cable provided. The monitors come with their USB-C, DisplayPort and HDMI cables. A cheap USB-C charging cable often carries no video at all.
- Be wary of docks for high resolutions. Many share the bandwidth between several outputs and throttle the monitor without saying so. For a first try in 5K or 6K, connect directly.
- Passive adapters do not convert. An HDMI-to-DisplayPort adapter does not turn one port into another: you need an active converter, and the bandwidth remains that of the weakest link.
- Length matters. Beyond two metres on DisplayPort or high-bandwidth HDMI, prefer a cable certified for the standard you are targeting.
The thirty-second check
Look at the port
A DisplayPort logo or a Thunderbolt lightning bolt next to the USB-C socket? Video will pass. Nothing at all? Check your machine's spec sheet.
Identify the HDMI version
On the machine as well as on the monitor. A 2.0 at both ends will limit you to 4K at 60 Hz, whatever the panel is capable of.
Check DSC on the graphics card side
Essential in 5K and 6K on a PC if you are going through DisplayPort 1.4. NVIDIA GeForce RTX and AMD Radeon RX 6000 and later support it.
Set the refresh rate after connecting
Windows often defaults to 60 Hz, even on a 165 Hz monitor. The setting is in Settings › System › Display › Advanced display settings.
FAQ
Connectivity: frequently asked questions
Can my USB-C port carry video?
Only if it supports DisplayPort Alt mode. Look for the DisplayPort logo or the Thunderbolt lightning bolt next to the port: a Thunderbolt 3, 4 or 5 port always carries video. On many laptops, only one USB-C port can.
DisplayPort or HDMI, which to choose?
DisplayPort as soon as you are aiming at a high refresh rate or a resolution above 4K: it offers more bandwidth and avoids questions of version. HDMI suits consoles and simple setups, provided you check whether it is a 2.0 or a 2.1.
What is DSC compression?
A visually lossless compression, handled by the graphics card, that allows a high resolution to pass through reduced bandwidth. It is what makes 5K and 6K possible over DisplayPort 1.4. A card that does not support it tops out at 4K.
Can a dock drive a 5K monitor?
Some can, many cannot. Docks often share bandwidth between several outputs and throttle the resolution or the refresh rate without warning. For a first connection, test directly before concluding that the monitor is at fault.
Is 100 W enough to charge my laptop?
Yes for a MacBook Air, a 14-inch MacBook Pro and most Windows laptops. On a machine whose original charger delivers more, charging is simply slower when the computer is working flat out.
The right cable, from day one
Every monitor comes with its USB-C, DisplayPort and HDMI cables. Delivery and after-sales service in Europe, 2-year warranty in the European Union.
See all Kuycon monitorsGuide written in August 2026. The bandwidth values are indicative; the exact connectivity is on each model's product page.