DisplayPort 1.4 max refresh rate at 1440p and 4K

DisplayPort 1.4 is enough for 1440p at 240 Hz and 4K at 120 Hz without compression, but only at 8-bit colour. At 10-bit colour neither fits: uncompressed 1440p stops at about 205 Hz and 4K at about 97 Hz. 4K at 144 Hz does not fit uncompressed at any bit depth. It needs DSC, or 4:2:2 colour at 8-bit. At 1080p, DP 1.4 carries up to about 406 Hz at 8-bit, so every common 1080p mode fits.

What DisplayPort 1.4 is, and what limits it

DisplayPort 1.4 is a version of VESA's DisplayPort standard, released on March 1, 2016. Its top link rate is HBR3, which means High Bit Rate 3. VESA's 2019 USB DevDays presentation lists HBR3 at 8.1 Gbps per lane. A full DisplayPort cable has four lanes, four data paths side by side.

Not all of that is picture. DP 1.4 sends 8 bits of data as 10 bits on the wire, a scheme called 8b/10b. DisplayPort.org puts its overhead at 20%. VESA's slide does the sum and calls the result the "total usable data transfer rate":

The pixel clock is how many pixels the link sends per second. It counts the visible pixels plus blanking, the unseen gap a video signal leaves around each line and each frame.

Two ways exist to fit a mode that is too big. DSC (Display Stream Compression) is VESA's compression standard, and VESA's slide lists it among the new features of DisplayPort 1.4. DisplayPort.org gives its typical ratio as "1:1 to about 3:1". It calls DSC visually lossless: a typical viewer "would in most cases not notice any difference". The other way is chroma subsampling. 4:2:2 sends colour detail at half the horizontal resolution, so 8-bit 4:2:2 needs 16 bits per pixel instead of 24. DisplayPort.org says DSC keeps image quality "unlike the use of chroma subsampling".

Every mode against DisplayPort 1.4

We calculated pixel clocks with an open implementation of VESA's CVT 1.2 timing formula, in reduced blanking v2 mode. It is the same method and the same clocks as our DisplayPort 1.2 page. The data rate is the pixel clock times 24 bits (8-bit) or 30 bits (10-bit).

Turned around, this gives the top refresh at each resolution. We stepped the refresh up one hertz at a time until the pixel clock passed 1080 MHz (8-bit) or 864 MHz (10-bit):

The payload is 1.5 times DisplayPort 1.2's 17.28 Gbps, so every top refresh is about 40 to 50% higher than on DP 1.2. With 4:2:2 at 8-bit, 4K 144 Hz needs 1306.2 x 16 = 20.90 Gbps and fits. At 10-bit 4:2:2 it needs 26.12 Gbps and misses by 0.8%.

Worked case: a 360 Hz 1440p monitor on an RTX 40 card

Take MSI's MAG 271QPX QD-OLED. MSI's datasheet lists "1 x DisplayPort (1.4a)" and, in its notes, "Display Port: 2560 x 1440 (Up to 360Hz)". It also gives the panel as "1.07B, 10 bits". Now suppose it is plugged into a GeForce RTX 4070. NVIDIA's spec page lists that card's ports as "DisplayPort 1.4a".

At 360 Hz the mode needs a 1640.4 MHz pixel clock. At 8-bit that is 39.37 Gbps, against 25.92 on the link. Could a monitor's own, shorter blanking close the gap? No. The visible pixels alone come to 2560 x 1440 x 360 x 24 = 31.85 Gbps, before any blanking at all. So MSI's 360 Hz figure over DP 1.4a can only work with DSC. The datasheet never names DSC, but the arithmetic leaves nothing else at full colour.

How hard does DSC work here? 39.37 / 25.92 is about 1.5:1 at 8-bit. At 10-bit, 49.21 / 25.92 is about 1.9:1. Both sit inside the "1:1 to about 3:1" that DisplayPort.org gives as typical. The same monitor lists "HDMI 2.1 (WQHD@360Hz)" as well. On a full-speed HDMI 2.1 link, 1440p 360 Hz fits uncompressed at 8-bit, as our HDMI 2.1 page shows. If DSC costs you a feature you use, that port is the one to try.

"1440p 240 Hz, 4K 120 Hz": right, but only at 8-bit

The short answer that circulates gives no bit depth. Cable Matters says DP 1.4 supports "4K resolution at up to 120Hz" and "can handle 240Hz on both 1080p and 1440p resolutions". The table agrees, at 8-bit. At 10-bit both claims fail.

KTC gets closer. It says 1440p 240 Hz at 10-bit "often" needs DSC. The arithmetic is firmer than "often". At 10-bit the visible pixels of 1440p 240 Hz come to 26.54 Gbps, more than 25.92 before any blanking. So no 10-bit 1440p 240 Hz signal fits DP 1.4 uncompressed, whatever the monitor's timing. The same holds for 4K 120 Hz at 10-bit (29.86 Gbps of visible pixels) and 4K 144 Hz at 8-bit (28.67).

The 8-bit answers are the close ones. 4K 120 Hz has 0.4% to spare at standard timing, and 1440p 240 Hz has 5%. Whether those fit uncompressed depends on the timing the monitor reports, not on the standard.

NVIDIA's own wording shows where the line sits. Its RTX 40 page gives the top as "4k 12-bit HDR at 240Hz with DP 1.4a + DSC". Its RTX 50 page lists "DisplayPort 2.1b with UHBR20" instead. That faster link is what lets an RTX 50 card skip DSC on some of these modes, if the monitor supports it too.

Where this stops applying

Every figure here assumes CVT reduced blanking v2 and four lanes at HBR3. Monitors ship their own timings, so the close cases can go either way: 4K 120 Hz and 1440p 240 Hz at 8-bit, and 4K 98 Hz at 10-bit. A link runs at its slower end. A DP 1.4 monitor on a DP 1.2 card gets 17.28 Gbps, and a monitor whose menu is set to DP 1.2 does too. USB-C often runs DisplayPort on two lanes, which halves the payload (USB-C max refresh rate covers that). A "DP 2.1" label does not promise a faster link either. DisplayPort.org says DP 2.1b certification needs "a minimum of HBR2 with DSC", plus at least one feature from a list. UHBR is one item on that list, not a requirement. What DSC switches off on NVIDIA cards is in our DSC article. The worked case is arithmetic, not a test of the MSI monitor or any card.

Sources

• VESA, DisplayPort Alt Mode over USB Type-C, USB DevDays 2019 (DP 1.4 release date, HBR3 rate, 25.92 Gbps usable rate, DSC as a DP 1.4 feature).
• DisplayPort.org, FAQ (8b/10b 20% overhead, DSC typical ratio and visually lossless definition, chroma subsampling, DP 2.1b certification minimum).
• kevinlekiller, CVT 1.2 modeline calculator (reduced blanking v2 timings, run for every mode here).
• NVIDIA, GeForce RTX 4070 family specifications (DisplayPort 1.4a, 4K 240 Hz with DSC).
• NVIDIA, GeForce RTX 5070 family specifications (DisplayPort 2.1b with UHBR20).
• MSI, MAG 271QPX QD-OLED datasheet (DisplayPort 1.4a, 1440p up to 360 Hz per input, 10-bit panel).
• Cable Matters, Does DisplayPort 1.4 Support 240Hz?, April 20, 2020.
• KTC, Can DisplayPort 1.4 Support 1440p at 240Hz Without Display Stream Compression?, May 20, 2026.