DisplayPort or HDMI: the right cable for 240 Hz

You bought a 240 Hz monitor, and Windows offers you 144. The panel is rarely the culprit. More often a cable or a port quietly caps the link, and the fix is often just a swap.

The short answer

DisplayPort or HDMI for 240 Hz? Our assessment: on a PC, DisplayPort is usually the first choice. NVIDIA's current cards have three DisplayPort outputs and one HDMI output, and VESA certifies cable classes for each speed tier [9][17]. HDMI 2.1 with an Ultra High Speed HDMI Cable carries up to 48 Gbit/s and is the port a console expects [12][19]. Whether a mode fits depends on resolution, refresh rate and colour depth. By our calculation, 2560×1440 at 240 Hz with 8-bit colour just fits DisplayPort 1.4 without compression, while 3840×2160 at 240 Hz needs Display Stream Compression (DSC) or DisplayPort 2.1 at UHBR20 [1][2][3][11]. Buy a certified cable for the tier you need, then check the mode that is actually running. We name no cable models and rank no products. All figures are as of 25 Oct 2026.

How it works

1. Work out what your mode needs. A monitor does not only receive visible pixels. Every line and every frame also carries a blanking interval. VESA's timing standard CVT defines a "reduced blanking v2" variant for flat panels: 80 extra pixels per line and a vertical blanking of at least 460 microseconds per frame [11]. The pixel clock is the total pixels per line times the total lines times the refresh rate. Multiply it by the bits per pixel, 24 for 8-bit RGB and 30 for 10-bit RGB, and you get the data rate. Here is the calculation as a short script, so you can check our numbers:

import math
def cvt_rb2_gbps(w, h, hz, bpp):
    h_total = w + 80                           # 80-pixel horizontal blanking
    line_time = (1 / hz - 460e-6) / h          # seconds per active line
    v_blank = max(math.floor(460e-6 / line_time) + 1, 15)
    pixel_clock = hz * h_total * (h + v_blank) # pixels per second
    return pixel_clock * bpp / 1e9

print(round(cvt_rb2_gbps(2560, 1440, 240, 24), 2))  # 24.62

Your monitor may use its own, tighter timing from its EDID data, so treat our results as a careful estimate, not a measurement. Our assessment: a mode within about five percent of a limit is borderline and may need DSC anyway.

2. Compare with what the link can carry. Each connection has a raw rate and a payload, the part left for audio and video after the line coding. DisplayPort 1.3 and 1.4 run HBR3 at 8.1 Gbit/s per lane, 32.4 Gbit/s over four lanes, which leaves a payload of 25.92 Gbit/s [1][2]. DisplayPort 2.x adds the UHBR rates with 128b/132b coding, which VESA puts at only 3 percent overhead instead of 20 percent [8]. At UHBR20 that gives a payload of 77.37 Gbit/s [3]. For UHBR10 and UHBR13.5, VESA names 40 and 54 Gbit/s as the four-lane maximum [5][6]. Scaled with the same ratio as VESA's 77.37 of 80, that is about 38.7 and 52.2 Gbit/s of payload. That scaling is our derivation, not a VESA figure. HDMI 2.1 offers up to 48 Gbit/s with its Fixed Rate Link signalling [12]. The public HDMI pages we checked do not state how much of that remains as payload. Microchip's documentation for its HDMI 2.1 transmitter IP names 16b/18b line coding for FRL, as described in the HDMI 2.1 specification [22]. By our calculation that leaves at most about 42.7 Gbit/s, before packet and error-correction overhead, so we use 48 only as an upper limit. HDMI 2.2 has been out since June 2025 and doubles this to 96 Gbit/s; it supports 4K at 240 Hz with full chroma at 10 and 12 bit without compression and needs the new Ultra96 HDMI Cable for that [13][14].

Which mode fits where (our calculation, CVT-RB2, RGB)

Read the HDMI column with care: it compares against the gross 48 Gbit/s, and the usable payload is lower. Against our 42.7 Gbit/s ceiling, 3440×1440 and 4K at 144 Hz with 10-bit colour already reach about 96 and 92 percent. The closer a value gets to 100 percent, the less certain it is that the mode runs without DSC. For 4K at 240 Hz with 10-bit colour, HDMI states that HDMI 2.2 carries it uncompressed [13]. Every row that does not fit uncompressed can still work with DSC, if card and monitor both support it.

3. Understand DSC instead of fearing it. Display Stream Compression is a VESA codec that compresses the signal between graphics card and monitor with low latency. VESA calls it "visually lossless", a claim backed by subjective tests with viewers [10]. For 24-bit colour it compresses 3:1 down to 8 bits per pixel, for 30-bit colour 3.75:1 [10]. DSC 1.2b is part of both DisplayPort and HDMI [10]. Applied to the hardest row of the table, our arithmetic gives about 18 Gbit/s for 4K at 240 Hz with 8 bits per pixel after compression, which fits even into DisplayPort 1.4. On NVIDIA cards, DSC over DisplayPort works from the GeForce RTX 20 and GTX 16 series, DSC over HDMI 2.1 from the RTX 30 series, and the driver switches it on automatically when the monitor supports it [15]. There is a catch with several screens: a DSC mode with a high pixel rate can occupy two of the GPU's internal display heads, so RTX 40, 30 and 20 cards may then drive only two displays at once [15][16]. NVIDIA names 3840×2160 at 160 Hz as an example of such a high-bandwidth mode [16].

4. Check what your graphics card offers. NVIDIA lists DisplayPort 2.1b with UHBR20 and HDMI 2.1b for the GeForce RTX 50 series, each up to 4K at 480 Hz with DSC [17]. AMD lists DisplayPort 2.1a and HDMI 2.1b for the Radeon RX 9070 series [18]. Neither that press release nor AMD's product page for the RX 9070 XT names a UHBR tier [18][23], so check the spec page of your exact board before you buy a DP80 cable. Our assessment: an older card with DisplayPort 1.4 is no reason to panic. From the GeForce RTX 20 and GTX 16 series on, it can use DSC and still reach most 240 Hz modes; NVIDIA warns that older cards such as the GTX 10 series may not reach a DSC monitor's highest refresh rate [15].

5. Pick the cable by certificate, not by the word on the bag. For DisplayPort, VESA certifies cable classes. Since DisplayPort 2.1a, DP54 cables carry UHBR10 and UHBR13.5 over up to two metres passively, and VESA has tested existing DP40 cables as compliant with DP54 [5]. DP80 cables carry up to UHBR20 and also UHBR13.5 [4]. Passive DP80 cables have been limited to about one metre, so DisplayPort 2.1b adds DP80LL, an active cable for UHBR20 over up to three metres [7]. You can search the certified cables by class in VESA's product database [9]. For HDMI, the Ultra High Speed HDMI Cable is the class for up to 48 Gbit/s. Its certification is mandatory, each package carries a certification label with a QR code you can scan, and the name must also be printed on the cable jacket [12]. Our assessment: a cable without a certificate entry or label is a gamble, however many "8K" stickers it has.

6. Connect PC and console to the same monitor. Sony states that the PS5 supports HDMI 2.1 and 4K at 120 Hz. It asks you to use the cable in the box or an Ultra High Speed HDMI Cable, to connect the console directly instead of through a receiver, and to use an HDMI 2.1 port on the display [19]. A sensible split is therefore: graphics card on DisplayPort, console on HDMI. Monitors do not always give every HDMI port the same capabilities, so check the manual to see which input accepts which mode. If you run several displays from an RTX 40, 30 or 20 card, NVIDIA notes that forcing a lower standard in the monitor's menu, such as DisplayPort 1.4 instead of 2.1, can free up capacity for more screens [16].

7. Check the mode that is actually running. On Windows 11 open Settings, System, Display, Advanced display. The information panel shows the current resolution and refresh rate and whether the display supports variable refresh rate. An asterisk next to a refresh rate means it does not work at the current resolution, and selecting it changes the resolution [20]. On Linux with an X11 session, xrandr lists each output's modes and marks the current one with * and the preferred one with +; xrandr --verbose prints more detail [21]. In a Wayland session, use your desktop's own display settings. If 240 Hz is missing, swap the cable for a certified one first. If that does not help, check the monitor's on-screen menu for its DisplayPort or HDMI mode [15].

A worked example

This is an invented setup, not a test. Lena has a 27-inch monitor with 2560×1440 at 240 Hz, one DisplayPort 1.4 input and two HDMI 2.1 inputs, a GeForce RTX 40 card and a PS5. The monitor's 10-bit mode would need about 30.8 Gbit/s by our calculation, which is more than DisplayPort 1.4 carries uncompressed. If the monitor supports DSC, the card switches it on; otherwise the 10-bit mode is out of reach on that input [1][2][15]. She connects the PC by DisplayPort and the PS5 by HDMI with the cable from the box [19]. Windows shows 144 Hz at first. In the Advanced display panel she sees that 240 Hz is offered only with an asterisk [20], swaps the old DisplayPort cable for a certified one from VESA's database [9], and gets 240 Hz at native resolution. Nothing in this example was measured.

Checklist

• Write down resolution, refresh rate and colour depth you want, then calculate the data rate with the script above.
• Compare it with the payload of your link: 25.92 Gbit/s for DisplayPort 1.4, 77.37 Gbit/s for UHBR20.
• Check whether graphics card and monitor both support DSC if the mode does not fit uncompressed.
• Look up the DisplayPort version and UHBR tier of your exact graphics card on the maker's spec page.
• Buy a DisplayPort cable only with a VESA entry in the needed class, DP54 for UHBR13.5 and DP80 for UHBR20.
• Scan the certification label of an Ultra High Speed HDMI Cable before you use it for a console.
• Connect the console directly to an HDMI 2.1 port, not through a receiver.
• Check the running mode in Windows under Advanced display or on Linux with xrandr.

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