is it possible to use 3x 1440p monitors at same time with Raspi4?

[Jehuty]

I want to use my Rasp-Pi-4 with three 1440p monitors at 60Hz. Ist that possible?
Is there a solution to connect the third one, to USB, GPIO or something else?

(had thought, i can use the daisychain feature of a Dell 2720DC, but that's not working with hdmi, but with Displayport only)

[thagrol]

A lot depends on what you want to display.

A few options:

Goolge for gertvga666 - a GPIO to VGA adapter. I've no idea if using it provides an additional screen or mirrors/disables the existing ones.

For USB there's displaylink but you'll need an early chipset as v2 onwards require encryption and aren't supported under linux. I'm not sure how good the drivers are for the v1 chipsets either.

Matrox used tomake a box that sat between your copmputer and multiple displays tp fake things. The computer would see a single large resolution display and the box would split that across the dislays. No idea if it's still available, whether itworked with linux, and whether it needed closed source drivers. It also wasn't cheap.

You might be able to cobble something together using a zeroW to drive the third screen and provide a remotely accessable display. That'll come with limitation though like the inability to drag windows to/from that screen and the need to specify that display when starting an application.

Lastly, if you're feeling very brave and don't need the USB host ports, a couple of people have desoldered the USB 3 IC to expose the PCIe bus. Again, hit google for more info.

Note: I've not tried any of the above so treat accordingly and please don't ask me for more detailed help.

[aBUGSworstnightmare]

I want to use my Rasp-Pi-4 with three 1440p monitors at 60Hz. Ist that possible?
Is there a solution to connect the third one, to USB, GPIO or something else?

(had thought, i can use the daisychain feature of a Dell 2720DC, but that's not working with hdmi, but with Displayport only)

only two monitors are supported; regardless of how many options (DSI/DPI/2x HDMI) you have (some combinations block each other, i.e. you can't use DSI + DPI together)

[thagrol]

I want to use my Rasp-Pi-4 with three 1440p monitors at 60Hz. Ist that possible?
Is there a solution to connect the third one, to USB, GPIO or something else?

(had thought, i can use the daisychain feature of a Dell 2720DC, but that's not working with hdmi, but with Displayport only)

only two monitors are supported; regardless of how many options (DSI/DPI/2x HDMI) you have (some combinations block each other, i.e. you can't use DSI + DPI together)

Does that still apply if max_framebuffers is increased above 2?

And does it apply to displaylink and vnc servers?

[cleverca22]

Goolge for gertvga666 - a GPIO to VGA adapter. I've no idea if using it provides an additional screen or mirrors/disables the existing ones.

at least on the rpi3 model, the pixel clock had an upper limit of 75mhz, not sure if the pixelclock for rpi4 has newer limits
some very rough math says that 2560x1440 would get 20fps at that rate, if you ignore all of the h/vsync and porch delays that slow it down more

only two monitors are supported; regardless of how many options (DSI/DPI/2x HDMI) you have (some combinations block each other, i.e. you can't use DSI + DPI together)

from what ive heard in other threads, the rpi4 has a hard limit of 3 active displays

you first have 3 channels on the HVS, that will composite together display lists and generate scanlines

you then have 5 pixel valves (max of 3 active at once), which read from an HVS channel (there is a limited selection for each PV), and manage all of the video timing

There are 3 HVS channels on all Pis.
Follow the pixel valve (controls the timing) config in https://github.com/raspberrypi/linux/bl ... vc4_crtc.c. struct vc4_crtc_data assigned to each compatible string.
Pi0-3 you have 3 pixel valves. The outputs of these can then be muxed to a fixed set of encoders.
Pi4 you have 5 pixel valves, so the HVS channels can be muxed between them (see the hvs_available_channels value). Generally they then feed a single encoder (limited output muxing - pv0 doing DSI0/DPI, and pv1 doing DSI1/SMI).

(from viewtopic.php?f=67&t=277092)

it sounds like PV0 for DPI wont conflict with the hdmi any, so you should be able to use a vga666 adapter to drive an analog display, in combination with 2 hdmi

if you can find a DPI panel of the desired resolution, you can also keep it digital and pure DPI like https://www.adafruit.com/product/2453

[drgeoff]

If the aim is to have the same content on the three monitors you can use something along the lines of https://www.amazon.co.uk/Splitter-Xbox3 ... B00LM4IJ60 or https://www.amazon.co.uk/dp/B07VNDK84Z

[jamesh]

Yes, cannot go more than 2. There are not enough pixel valves to go to 3, unless we use the one that is usually used for transposing. That might be possible in KMS, but still only gives you, IIRC, 2xHDMI + 1xDSI/DPI. Maybe composite? BUT none of this is implemented, so not at present, or in the nr future.