DisplayPort 1.2 max refresh rate at 1440p
DisplayPort 1.2 runs 1440p at 165 Hz at 8-bit colour, and tops out at about 174 Hz. It cannot run 1440p at 240 Hz, and it has no compression to fall back on. The top refresh at each resolution, at 8-bit and 10-bit, from the same formula as our HDMI 2.0 page.
DisplayPort 1.2 is enough for 1440p at 165 Hz at 8-bit colour, and the top is about 174 Hz. It is not enough for 1440p at 240 Hz. At 1080p it carries up to about 288 Hz, and at 4K up to about 81 Hz. At 10-bit colour the 1440p top falls to about 141 Hz. There is no compressed mode to fall back on, so anything past those limits needs DisplayPort 1.4 or HDMI 2.1.
What DisplayPort 1.2 is, and what limits it
DisplayPort 1.2 is the version that introduced the HBR2 link rate. HBR2 means High Bit Rate 2. VESA's 2019 USB DevDays presentation lists it at 5.4 Gbps per lane. A full DisplayPort cable has four lanes, which are four separate data paths running side by side.
Not all of that is picture. DisplayPort 1.2 sends 8 bits of data as 10 bits on the wire, a scheme called 8b/10b. The same VESA slide gives the formula for DisplayPort 1.4: lane rate, times 0.8 for the encoding, times four lanes. Apply it to HBR2 and you get the DP 1.2 payload, the rate left for the picture:
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.
DSC (Display Stream Compression) is how newer links squeeze in modes that do not fit. VESA's slide lists DSC among the new features of DisplayPort 1.4. DisplayPort 1.2 does not have it. So on DP 1.2 a mode either fits uncompressed or it does not run.
Every mode against DisplayPort 1.2
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 HDMI 2.0 page and our DSC and bandwidth article. The data rate is the pixel clock times 24 bits (8-bit) or 30 bits (10-bit).
| Mode | Pixel clock (MHz) | 8-bit (Gbps) | 10-bit (Gbps) | DP 1.2 at 8-bit | DP 1.2 at 10-bit |
|---|---|---|---|---|---|
| 1080p 240 Hz | 583.2 | 14.00 | 17.50 | Fits | No, by 1.3% |
| 1440p 120 Hz | 483.1 | 11.59 | 14.49 | Fits | Fits |
| 1440p 144 Hz | 586.6 | 14.08 | 17.60 | Fits | No, by 1.9% |
| 1440p 165 Hz | 679.1 | 16.30 | 20.37 | Fits, 6% to spare | No |
| 1440p 170 Hz | 701.5 | 16.84 | 21.04 | Fits, 3% to spare | No |
| 1440p 180 Hz | 746.1 | 17.91 | 22.38 | No, by 3.6% | No |
| 1440p 240 Hz | 1025.8 | 24.62 | 30.77 | No | No |
| 3440x1440 100 Hz | 531.5 | 12.76 | 15.95 | Fits | Fits |
| 3440x1440 144 Hz | 782.1 | 18.77 | 23.46 | No | No |
| 4K 60 Hz | 522.6 | 12.54 | 15.68 | Fits | Fits |
| 4K 120 Hz | 1075.8 | 25.82 | 32.27 | No | No |
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 720 MHz (8-bit) or 576 MHz (10-bit):
| Resolution | 8-bit (Hz) | 10-bit (Hz) |
|---|---|---|
| 1920 x 1080 | 288 | 237 |
| 2560 x 1440 | 174 | 141 |
| 3440 x 1440 | 133 | 107 |
| 3840 x 2160 | 81 | 65 |
The payload is a fifth more than HDMI 2.0's 14.4 Gbps, so every top refresh here is higher than on the HDMI 2.0 page. The 4K row matches VESA's own table, which lists 4K at 60 Hz for HBR2.
Worked case: a 170 Hz 1440p monitor on a DisplayPort 1.2 card
A Tom's Hardware forum thread asks this exact question. The poster weighed a 170 Hz 1440p monitor against a 144 Hz one, believing DP 1.2 "supports upto 144fps at 1440p". Here is how the numbers decide it.
Suppose the card and monitor both run DisplayPort 1.2 at HBR2. At 170 Hz the mode needs a 701.5 MHz pixel clock. At 8-bit that is 701.5 x 24 = 16.84 Gbps. The link carries 17.28. The mode fits, with about 3% to spare. So the 170 Hz monitor is worth buying for this card.
Now suppose 10-bit colour is set in the graphics driver. At 170 Hz the mode needs 21.04 Gbps, and it will not fit. The 10-bit ceiling at 1440p is about 141 Hz, so even 144 Hz misses. If the top refresh on offer looks too low, set 8-bit first.
144 Hz or 165 Hz, 21.6 or 17.28: which is right
Two refresh answers circulate. The Tom's Hardware poster had read 144 Hz. A reply in the same thread said HBR2 "should push 1 1440p monitor to at least 165". KTC's 2026 post calls 1440p 165 Hz at 8-bit "usually workable, near the limit" on DP 1.2.
The arithmetic says 165 Hz is right, at 8-bit, with 6% to spare. Dell says the same of a real monitor: its community manager wrote that the S2417DG on "DP 1.2 can do 2560x1440 60Hz/85Hz/100Hz/120Hz/144Hz/150Hz/160Hz/165Hz". 144 Hz is a mode that fits, not the ceiling. The 144 figure does hold for one case: at 10-bit, 1440p stops at 141 Hz.
The bandwidth figures clash the same way. 21.6 Gbps is the raw rate, all four lanes counted. 17.28 Gbps is what is left after 8b/10b, and only that figure decides which modes fit. Divide 21.6 by 24 and you would expect 1440p at about 213 Hz. No DP 1.2 link carries that.
A third answer is too low. In an Acer community thread titled "Stuck at 120hz", an XV272U owner on a GTX 660 could not get past 120 Hz. One reply said DP 1.2 "gives a maximum output of 4K at 30Hz". VESA's table says HBR2 carries 4K at 60 Hz. 4K at 30 Hz is what the older HBR rate carries, the top rate before DisplayPort 1.2. So the 120 Hz cap in that thread did not come from the DP 1.2 standard. By the arithmetic, a DP 1.2 link at HBR2 carries 1440p 144 Hz at 8-bit.
Why a monitor set to DP 1.2 caps lower
Many monitors have a DisplayPort version setting in their on-screen menu (OSD). That setting decides which version the monitor offers the graphics card. The card then trains the link at that version's rate.
Set a DP 1.4 monitor to DP 1.2, and the link drops to HBR2 and 17.28 Gbps. It also gives up DSC, a DP 1.4 feature. A 1440p 240 Hz monitor on that setting cannot pass about 174 Hz at 8-bit. The card can only pick from the modes on the monitor's own list that fit, so the top you see may be lower still. A 180 Hz monitor misses 180 Hz by 3.6%.
Set it to an older version, and it is worse. The older HBR rate is 2.7 Gbps per lane in VESA's table, which by the same formula is 8.64 Gbps of payload. That carries 1440p to about 90 Hz at 8-bit. Dell's support note shows the effect. A Dell 4K or 2K display may report "WQXGA 2560 x 1600" as its top resolution, which is the top of VESA's HBR row. The fix Dell gives is to "configure DisplayPort input to DisplayPort 1.2" in the OSD. So if a fast monitor is stuck low on DisplayPort, check that menu before you buy a cable.
Where this stops applying
Every figure here is full RGB colour (4:4:4) at CVT reduced blanking v2. Monitors ship their own timings, so the close cases can go either way: 1440p 170 Hz at 8-bit, and 1440p 144 Hz and 1080p 240 Hz at 10-bit. Chroma subsampling, which sends less colour data, is not covered. A link runs at its slower end, so a DP 1.4 monitor on a DP 1.2 card gets 17.28 Gbps. The graphics card only offers modes the monitor reports, so the monitor's spec sheet for that input still decides. USB-C is narrower: VESA says two-lane DP 1.2 over USB-C gives "Two 1080p displays, or one 4k@30Hz". The worked case is arithmetic, not a test of any card or monitor. For what each refresh step is worth once it runs, see the refresh rate guide.
What DisplayPort 1.2 carries
- DP 1.2 is 21.6 Gbps raw, 17.28 Gbps of picture: a 720 MHz pixel clock at 8-bit, 576 MHz at 10-bit.
- 1440p: 165 Hz and 170 Hz fit at 8-bit. The top is about 174 Hz. 180 Hz and 240 Hz do not fit.
- At 10-bit the top is 237 Hz at 1080p, 141 Hz at 1440p and 65 Hz at 4K.
- No DSC on DP 1.2. A monitor set to DP 1.2 in its menu loses DSC too.
- Past these limits, change the link to DP 1.4 or HDMI 2.1, and the cable to match (which DisplayPort cable).
Sources
- VESA, DisplayPort Alt Mode over USB Type-C, USB DevDays 2019 (link rate table, 25.92 Gbps payload formula, DSC in DP 1.4, two-lane DP 1.2 over USB-C).
- kevinlekiller, CVT 1.2 modeline calculator (reduced blanking v2 timings, run for every mode here).
- Dell, DisplayPort settings of the LCD display may limit resolution, article 000129296.
- Dell Community, S2417DG DP Hz, answer by DELL-Chris M, April 23, 2023.
- Tom's Hardware forums, Max Refresh Rate for a Display Port 1.2 equipped 1440p monitor?, November 26, 2022.
- Acer Community, Stuck at 120hz Acer Nitro XV272U, June 2021.
- KTC, Can DisplayPort 1.2 Handle 1440p 165Hz, or Do You Need 1.4?, June 11, 2026.
Frequently asked questions
Can DisplayPort 1.2 do 1440p 165 Hz?
Yes, at 8-bit colour. At standard reduced blanking the mode needs a 679.1 MHz pixel clock, or 16.30 Gbps. DisplayPort 1.2 carries 17.28 Gbps of picture data, so the mode uses 94% of it. At 10-bit it needs 20.37 Gbps and does not fit.
Can DisplayPort 1.2 do 1440p 144 Hz?
Yes, at 8-bit, with room to spare: 14.08 Gbps against 17.28. At 10-bit it needs 17.60 Gbps, which is just too much. At 10-bit, 1440p tops out at about 141 Hz on DisplayPort 1.2.
Can DisplayPort 1.2 do 1440p 240 Hz?
No. The mode needs a 1025.8 MHz pixel clock, 24.62 Gbps at 8-bit, which is 42% more than DisplayPort 1.2 carries. DP 1.2 has no DSC, so there is no compressed mode either. Use DisplayPort 1.4 or HDMI 2.1.
Is DisplayPort 1.2 21.6 Gbps or 17.28 Gbps?
Both, measured at different points. 21.6 Gbps is the raw rate on the wire: four lanes at 5.4 Gbps. Two bits in every ten are encoding overhead, so 17.28 Gbps is left for the picture. Only the 17.28 figure tells you which modes fit.
Can DisplayPort 1.2 do 4K 60 Hz?
Yes, at 8-bit and at 10-bit. 4K 60 Hz needs 12.54 Gbps at 8-bit and 15.68 Gbps at 10-bit, both under 17.28. VESA's own table lists 4K at 60 Hz for the HBR2 rate that DisplayPort 1.2 introduced. 4K 120 Hz does not fit.