Does 1440p at 360 Hz or 480 Hz need DSC, and should I use DisplayPort or HDMI?

For 1440p at 480 Hz, yes: every common link needs DSC except DisplayPort 2.1 at UHBR20. For 1440p at 360 Hz, it depends on the port: DisplayPort 1.4 needs DSC, HDMI 2.1 carries it uncompressed at 8-bit colour. Use DisplayPort when both ends support UHBR20; otherwise use whichever port runs your mode without compression.

Every mode against every link

The data rate a mode needs is its pixel clock times the bits per pixel: 24 for 8-bit RGB, 30 for 10-bit. The pixel clock includes blanking as well as visible pixels. We calculated it with an open implementation of VESA's CVT 1.2 formula in reduced blanking v2 mode, which uses 80 pixels of horizontal blanking and a minimum vertical blank of 460 microseconds.

Links are compared on payload, the rate left after line encoding:

The 48 Gbps is HDMI.org's maximum for HDMI 2.1 systems, and TFTCentral gives its 16b/18b encoding as 88.8% efficient, about 42.6 Gbps usable. VESA rates DP40 cables at UHBR10, "providing a maximum throughput of 40 Gbps", and DP80 at UHBR20 for 80 Gbps. DisplayPort.org states the 77.37 Gbps UHBR20 payload and puts 8b/10b overhead at 20%. KTC gives the same 32.4 and 25.92 for DisplayPort 1.4, and says 1440p 240 Hz fits without DSC at 8-bit but often not at 10-bit. Our row agrees.

DisplayPort or HDMI: the surprise at 360 Hz

The common advice is "always use DisplayPort", and for UHBR20 it is right: 77.37 Gbps carries every mode here uncompressed. But DisplayPort 1.4 has 25.92 Gbps of payload and HDMI 2.1 has 42.67. Between those two, HDMI is the bigger pipe by about 65%.

That matters at 1440p 360 Hz. Over DisplayPort 1.4 the mode needs DSC at about 1.5:1. Over HDMI 2.1 at 8-bit it fits, using 92% of the payload. If DSC costs you a feature you use (see below), HDMI 2.1 is the better port here.

At 1440p 480 Hz there is no such choice. Even the active pixels alone, with zero blanking, come to 42.47 Gbps at 8-bit, and a real signal cannot have zero blanking. HDMI 2.1 needs DSC, DisplayPort 1.4 needs DSC at about 2.2:1, and only UHBR20 runs it native. The same is true of 4K 240 Hz.

How much compression is that?

VESA says DSC "can reduce DisplayPort transport bandwidth in excess of 67 percent without visual artifacts", which is 3:1. DisplayPort.org gives the typical ratio as "1:1 to about 3:1" and defines visually lossless as a typical observer under typical viewing conditions who "would in most cases not notice any difference". Every mode here needs less than 3:1, so image quality is not the reason to avoid DSC.

What DSC switches off

The real cost is features. NVIDIA's wording, quoted by TFTCentral: DSR, DLDSR and NVIDIA Image Scaling "are supported when DSC mode is enabled, if the pixel rate needed to drive the display mode does not exceed the GPU's single head limit. If GPU uses two or more internal heads to drive the display", those features "are not supported". TFTCentral reports NVIDIA gave no simple rule for telling which applies, since it depends on the monitor's EDID timings.

If you rely on DLDSR, prefer a link that runs your mode without DSC. If you do not, DSC at these ratios has no cost we can source.

Where the table stops applying

Pixel clocks are CVT reduced blanking v2. Many monitors ship their own timings, often with shorter vertical blanking, and the 460 microsecond minimum is a large share of a 2.08 ms frame at 480 Hz. The borderline case is 1440p 360 Hz on UHBR10: 39.4 Gbps at CVT timing against 38.69 of payload, with the active pixels alone at 31.9. Whether it fits depends on the monitor's own blanking.

A link is the lower of its two ends: a UHBR20 monitor on a DisplayPort 1.4 card gets 25.92 Gbps. Check the refresh the monitor's spec sheet lists per input, not the port version on the box.

HDMI.org now lists HDMI 2.2 at up to 96 Gbps with an Ultra96 cable. The table uses HDMI 2.1.

Before paying for 480 Hz at all, check that you can feed it. The refresh rate guide shows how little each step above 240 Hz saves. The FPS and refresh calculator tests your own 1% lows against it, and only a panel with fast enough pixels can show those frames distinctly, which is the case OLED makes over IPS. If the framerate is not there, dropping to 1080p is the cheaper lever, as the resolution guide explains, and it also brings every 1080p mode up to 360 Hz inside DisplayPort 1.4 at 8-bit.