Interlaced resolutions not supported on ARC A380 (HDMI and DP)

[Slay3rOne]

Hi. I spent a lot of time searching on the various forums for reports on whether or not Intel ARC GPUs would support interlaced output or not. I have only seen contradictory answers to that question from various users, a question that has been asked a few times already in the past.

I've read a few official answers on this very forum stating that Intel ARC GPU does support interlaced resolutions "as long as the display supports it".

I understand this is a very niche use case, but interlaced resolutions are working on Intel Integrated Graphics. So I decided to go ahead and just purchase a ARC A380 for the purpose of testing this myself and have a definitive answer. If it works, I would of course keep it, if not, I might return it or wait until interlaced resolutions support gets added in futur driver versions, maybe.

I just received my GPU and unfortunately, I am here to report that interlaced resolutions does not work at all, at least not with the latest drivers 31.0.101.5382 I installed yesterday.

The various displays I am using supports any random interlaced resolution over either HDMI or DisplayPort up to 540MHz bandwidth.

I tested and confirmed interlaced resolutions to be working on the Intel UHD Graphics 630 of the Core i7 9700K, both through HDMI and DisplayPort. Nothing at all on the Intel ARC A380.

For reference, I tested the following resolutions:

• 1920x1440i 170Hz
• 1600x1024i 160Hz
• 1200x1200i 209Hz

So obviously the Intel ARC GPUs does not support interlaced resolutions at all on Windows. Is there a known previous driver version that has support for interlaced resolutions available by any chance?

I don't need any specific recent driver game optimisations, as my goal here is to use this GPU for video output only, alongside a higher end NVIDIA RTX 3080 (5080 in the future) for rendering.

Thank you!

[RamyerM_Intel]

Hello Slay3rOne, 

Thank you for posting in the communities. I want to let you know that the integrated Intel® Arc™ Graphics do support interlaced mode through native HDMI as long as the display's panel supports it, however , for Intel® Arc™ A380 Graphics and A-Series Desktop graphics (codename Alchemist) interlaced resolutions are not supported. You may visit this link for more information: Does Intel® Arc™ Graphics Support Interlaced Resolutions? I know this is not the answer you are hoping for, but since the Arc A380 uses PCON to convert a DP signal to HDMI, it will not be able to support interlaced resolution.

Ramyer M. 

Intel Customer Support Technician 

[Slay3rOne]

Hello.

Thank you for your answer. I did not see that article, thanks for sending it to me.

Now, despite what is said on this. I spent some more time doing testing on the ARC A380, and I was in fact able to prove the opposite... Intel ARC A380 hardware definitely can output interlaced resolutions on either HDMI or DisplayPort, with early release driver versions.

I went back to the earliest driver supporting the A380, which is version 30.0.101.1736. And with this one, when applying custom interlaced resolutions with CRU (Custom Resolution Utility, by ToastyX), it shows up fine in Windows display adapter properties.

Interlaced resolutions were tested on my Sony GDM-F520 CRT monitor using CVT timings (170Hz max vertical, 137kHz max horizontal, 655+MHz pixel clock), using a LK7112 based adapter for HDMI to VGA (around 400-413MHz VGA bandwidth for my sample), and a Sunix DPU3000 for DisplayPort to VGA (540MHz VGA bandwidth).

I can report that interlaced resolutions did work on HDMI but after my first tests, trying to go past 1920x1080i at 60Hz the resolutions did not show up anymore in the display settings. That might be due to a mistake on my side, but I had some issues with HDMI from the start even outside of that testing and with the latest drivers (even on regular recent IPS monitors), so I did not spend more time investigating HDMI and moved to DisplayPort.

On DisplayPort, there was no limitation setting custom resolutions, 1920x1440i at 170Hz was showing up the the settings just fine. But the issue here is, going after a certain point, the displayed picture started to get completely messed up.

• At 1920x1440i, the highest 100% working refresh rate was 110.33Hz (221.71MHz pixel clock)
• At 1600x1200i, it was 154.46Hz (223.63MHz pixel clock, a bit higher for some reason, limitation might not be pixel clock then)
• Also tested 2880x1800i at 60Hz, working fine very close to the Intel ARC limit as well (still far from the monitor limit of 140Hz...)

That said, I also had issues sometimes on DisplayPort, with the monitor being disconnected when switching resolutions sometimes. All I add to do was to unplug and replug the VGA and maybe the adapter as well, and it was good to go again. Probably not something that would cause issues in normal use. Also, this is the earliest driver version available, and drivers have improved a lot during that time. Using old drivers is not something I would recommand at all, this was just for testing. Also, I only planned on using the GPU for passthrough, with a Nvidia RTX card used to render games, if tests were conclusive.

In the current state of things, if someone wants to output "standard" interlaced reslutions like 1080i (or maybe 480i? untested), this Intel ARC A380 could be an option to consider (though with early drivers it looks like, interlaced support has been dropped after).

Now if, like me, the goal is to push a CRT monitor to its limits and output very high resolutions at their maximum refresh rates, unfortunately this is definitely not a good choice at all, at least in this current state. If interlaced support is added back in the future, and limits were only software and can be adressed, then it could potentially become a viable option in the future. To be continued.

[RamyerM_Intel]

Hello Slay3rOne, 

We appreciate your patience and sincerely apologize for the delay in our response, as we have been in a detailed consultation with our engineering team to ensure a thorough investigation.

We understand the importance of addressing your concerns. Our findings indicate that due to the increasing rarity of CRT displays and our commitment to resolving the most pressing issues, we have adjusted our priorities accordingly. While we recognize the inconvenience this may cause, we suggest exploring alternative display options as a temporary measure. Please rest assured that while immediate action on CRT-related issues may not be feasible, we remain dedicated to providing quality support and will revisit this matter when possible.

With this in mind, I will proceed with closing this case. However, should you encounter any other issues or have further inquiries, please feel free to initiate a new thread, as we will no longer be monitoring this one.

Thank you for your patience and understanding.

Ramyer M. 

Intel Customer Support Technician