Understanding DP1.2 support for multiple monitors

I'm trying to understand the supported screen configurations for an Intel HD graphics integrated chip.

From everything I can see DP1.2 is supported, with support for up to 3 displays and support for 4k Video. In the documentation I've found it suggests that a max resolution of 4096x2304@60Hz is supported (for the Intel® HD Graphics 515 chip).

What is not clear to me is how this breaks down as you introduce multiple monitors. I currently have an ultrawide monitor at 3440x1440 and the laptop monitor at 1366x768. I'd like to add a 3rd monitor but it's not clear to me what resolutions I could effectively run.

Is the 4096x2304 indicative of the total pixels I can support (9437184) - and can I get more if I drop to 30Hz?

Thanks

My educated guess is that you can use another display similar to your own.

Here’s why, based on the Wikipedia DisplayPort page:

You have DisplayPort 1.2. This means you have HBR2 (High Bit Rate), which can deliver 5.4 GBit/s per lane. DisplayPort has 4 lanes.

If we slap your existing display’s resolution in some video timing calculator, we can deduce it requires roughly 7.5 GBit/s, with 8b/10b encoding that’s ~9.4 GBit/s. It fits in two lanes, but that’s really up to the display.

If you have two free lanes, you could use another similar screen. You can experiment with the timing calculator to find out. The “Total BW” row is the deciding factor. You can also look at the “DisplayPort HBR (2.7 GHz)” row, because the older version offers exactly half the bandwidth.

The effective data bandwidth of HBR2 lanes with 8b/10b taken into account is 4.32 GBit/s.

Your laptop display does not count in bandwidth calculations because it uses a different output on the GPU. It does count against the active screen total.

If your current display does not have a DisplayPort-Out connector, you may have to get a DisplayPort MST Hub.