OS/2, eCS & ArcaOS - Technical > Hardware

Display-port and HDMI

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Roderick Klein:

--- Quote from: Doug Bissett on October 28, 2021, 08:06:52 am ---Some years ago, I played with HDMI, and Display Port, on my Lenovo ThinkPad T510, and L530. I don't recall having any video problems using a TV as a screen. You do need to know how to switch, using the Fn key combination, and that probably needs to be done BEFORE starting to boot OS/2.

--- End quote ---

Some laptops in the BIOS still support this functionality to use the Fn keys to switch to the external display port when the ArcaOS has not yet started.

Note that on systems booted in UEFI mode this functionality is gone. Its not part of the UEFI specs best I can tell!

And you will need with UEFI boot a video driver that talks to the video chipset directly to be able to switch.

Roderick

Eugene Tucker:
Thank you to all for your responses I will be experimenting with my system.

Neil Waldhauer:

--- Quote from: Andi B. on October 28, 2021, 09:16:31 am ---DisplayPort works and is preferred.

But as usual with OS/2 it depends on what the BIOS offers. I talk about Panorama as SNAP only supports very old hardware. Usually the BIOS scans on which connector which monitor is attached and makes some decisions. Means if you have a monitor attached on DisplayPort it uses it. If you have a monitor attached at HDMI BIOS uses it. If there are monitors attached to both interfaces usually DP is preferred. There are also some settings in BIOS which affect which interface should be preferred and used. This is all done long before any driver (gengradd) is involved. So boot up (cold boot) after all cables are in place. Don't expect switching between interfaces on the fly with CTRL-ALT-DEL only.

Usually DisplayPort supports all resolutions while on older systems HDMI is not able to support f.i. 4k/60Hz even when the graphic chip can do it.

Another question is - will the BIOS offer the capabilities it detects from the interface, the monitor and the graphic chip in a form Panorama can use it? It depends. I've a system with build in Intel graphic and DP, HDMI and analog interfaces. It can handle 4k / 60Hz on DP and Win can use it. On HDMI only 4k / 30Hz is possible as HDMI at that time could not handle the necessary bandwidth and the BIOS knew this. Of course these modes work in Win. But the BIOS does not offer these capabilities in a form Panorama can use it. No more than WQHD was possible. So I had to install a PCIe graphic card with an integrated BIOS which does it right. DP works fine on this.

--- End quote ---

This agrees with my experience. I have many systems with DisplayPort, and all work as well as the VGA. Sometimes there is an additional resolution available with DisplayPort. But my monitor is inadequate to test the higher than HD resolutions.

Your information also suggests that Ctrl-Alt-Del will find new resolutions in a future ArcaOS system that supports UEFI. This needs to be tested, of course.

Lars:

--- Quote from: Roderick Klein on October 28, 2021, 09:23:21 am ---Note that on systems booted in UEFI mode this functionality is gone. Its not part of the UEFI specs best I can tell!

And you will need with UEFI boot a video driver that talks to the video chipset directly to be able to switch.

Roderick

--- End quote ---

I wonder if there is something like a standard UEFI video driver providing standard services (much like the legacy BIOS) and that has an interface that could be invoked by an OS video driver.
One of the problems would be that UEFI services and drivers are all 64-bit code (as far as I know). I don't know how you would call 64-bit code from 32-bit code (or even 16-bit code).

Roderick Klein:
Basically from what I can tell you have UEFI video services. But once the system boots and the OS takes over, you are left with a video framebuffer at a fixed resolution to write to.
Unless you have a native video driver to talk to the chipset.



Roderick

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