HDMI 2.1 UHD 144Hz - Arc A750 / A770

[captchasucks]

The specifications page for Arc A750 and A770 claims they have HDMI 2.1 but also state "Max Resolution (HDMI)‡ 4096 x 2160@60Hz" which is a contradiction if i'm not mistaken. I would buy it, if it can actually spit out 3840x2160 @ 120Hz or preferably 144Hz. Can anyone confirm whether the HDMI port is actually able to do that?

[MUC · Accepted solution]

Short answer: Use DisplayPort for 144 Hz. You can use HDMI port for 120 Hz.

Background:

It depends on the product. The DG2/Alchemist architecture delivers a maximum of 4K DCI (4096 x 2160) @ 60Hz natively from the GPU via HDMI, corresponding transmission via Transition Minimized Differential Signaling (TMDS). However, if the card manufacturer uses an additional Protocol Converter (PCON) chip on the Printed Circuit Board (PCB) which can convert DisplayPort signals from the GPU, then an HDMI 2.1 signal is available at the HDMI port of the graphics card. In this case it’s a transformation from Coordinated Video Timing (CVT-RB v2) according to Video Electronics Standards Association (VESA) for the DisplayPort interface into HDMI signaling using the Fixed Rate Link (FRL) principle.

Such PCON chips are applied by default on Intel’s own Arc A7x0 Limited Edition cards. And as far as I know also on all Graphics Add-in Boards (AIB) made by partner manufacturers like ASRock.

The PCON used in this architecture is the Realtek RTD2173.

https://www.techpowerup.com/review/intel-arc-a750/4.html

With other products, it is up to the manufacturers whether they use the PCON or not. The technical information provided by the graphics card maker must be carefully checked. If this PCON is implemented, an output of 4K DCI @ 120 Hz or 8K UHD @ 60 Hz is possible via HDMI. Low budget cards based on the A380 and below typically don't provide HDMI 2.1 FRL but only HDMI 2.0b (4K @ 60 Hz TMDS). ASRock Arc A750 Challenger (90-GA3HZZ-00UANF) is offering both. One connector HDMI 2.1, one connector HDMI 2.0b.

However, HDMI interfaces (should) comply with the standards determined by the Consumer Technology Association (CTA) for implementers to refer to CTA‐861 document “A DTV Profile for Uncompressed High‐Speed Digital Interfaces”. Current version is CTA-861-H. The previous version “G” can be viewed here: https://web.archive.org/web/20171201033424/https://standards.cta.tech/kwspub/published_docs/CTA-861-G_FINAL_revised_2017.pdf

This document defines certain Video Identification Codes (VIC) for a specific video format with its exact video timing including standard resolutions and refresh rates. The Extended Display Identification Data (EDID) is used by a display device to tell its link partner transmitter what parameters to use. And so, it will establish an appropriate connection. This is called "link training”.

144 Hz is not clearly defined in the above mentioned HDMI regulation. There is no VIC for that. Although it is technically possible, it requires adapted EDID information to actually establish a connection. For compatibility reasons, you shouldn't rely on this until CTA has defined and published appropriate standards for HDMI. So I don't think 144 Hz will work with HDMI plug & play. 120 Hz shouldn't be a problem though. Intel Arc DG2/Alchemist can output 10 bpc HDR via the PCON @ 4K 120 Hz RGB 4:4:4.

With VESA CVT-RB v2 over DisplayPort:

4K 144 Hz RGB 4:4:4 8 bpc ... OK

4K 144 Hz RGB 4:4:4 10 bpc ...

• DisplayPort 1.4a HBR3 only using Display Stream Compression (DSC)
• Due to theoretical calculation for DisplayPort 2.0 UHBR10 uncompressed, 144 Hz is still a bit too demanding (101 % bandwidth need). Intel Arc is designed for DP 2.0 UHBR10, but certification is still pending VESA CTS release

Remark: VESA Display Stream Compression (DSC) is part of both standards: DisplayPort 1.4a AND HDMI 2.1. It is supported starting with 11th Generation Intel Core Processor Graphics (also known as Tiger Lake) and newer. Depending on the system it may be necessary to explicitly allow it. A corresponding transferable guide can be found here:

https://www.dell.com/support/kbdoc/en-us/000197102/how-to-enable-display-stream-compression-on-latitude-precision-and-xps

If the source is basically capable of DSC an HDMI display device must enable it by transferring the needed parameters via EDID in the link training process. These parameters for DSC are contained in the CTA-861 Extension Block for "HDMI Forum Vendor Specific" and cover the following being enabled/disabled or specified (last 3 ones):

• main flag to enable DSC
• 10 bpc
• 12 bpc
• 16 bpc
• 1p2 (1.2V electrical voltage)
• All bpp
• DSC native YCbCr 4:2:0
• maximum FRL Rate (one of the following options which means Gbps per lane)
  • no support for compressed video transport
  • 3 Gbps
  • 6 Gbps 3 lanes
  • 6 Gbps 4 lanes
  • 8 Gbps
  • 10 Gbps
  • 12 Gbps
• maximum slices (one of the following options)
  • VESA DSC 1.2a is not supported
  • up to 1 slice and up to (340 MHz/KSliceAdjust) pixel clock per slice
  • up to 2 slices and up to (340 MHz/KSliceAdjust) pixel clock per slice
  • up to 4 slices and up to (340 MHz/KSliceAdjust) pixel clock per slice
  • up to 8 slices and up to (340 MHz/KSliceAdjust) pixel clock per slice
  • up to 8 slices and up to (400 MHz/KSliceAdjust) pixel clock per slice
  • up to 12 slices and up to (400 MHz/KSliceAdjust) pixel clock per slice
  • up to 16 slices and up to (400 MHz/KSliceAdjust) pixel clock per slice
• maximum total chunk [kilobytes] 

On my test device NUC11TNKv7 Win 11 22H2 operating Intel Iris Xe (Tiger Lake-UP3 - GT2) it was necessary to provide the flag for “All bpp”, otherwise there was no DSC.

For the sake of completeness be aware that if DSC is once enabled (basic capability of the source like in link above and EDID authorized by display) it may also be used for signal transmission that actually wouldn’t require DSC and could also be transmitted uncompressed.

VESA Display Stream Compression Standard (DSC)

Essentials of DisplayPort Display Stream Compression (DSC) Protocols

Essentials of DisplayPort Protocols at HBR3 Link Rates

Essentials of HDMI Fixed Rate Link Protocols

[captchasucks]

Thank you for the very elaborate answer.

I suppose the specifications pages are just for the chip, not for the limited edition A7x0 cards then, which lead to my confusion.
Intel should provide specs for those cards, or make it more obvious, if they already exists.

I would use display port, if my monitor had more than just the one, which is already occupied by another system.
So there are only two HDMI 2.1 ports left, that's why i'm in search for an upgrade.
144 Hz would be nice, but 120 is still OK.
Well, i'll order an A750 LE then, even though it'll be overkill for the purpose of that system.

[TinkerD]

I successfully obtained 8K@60 display mode using the HDMI port of my Intel Arc A750 Limited Edition Graphic card and an HDMI ultra high speed cable connecting to my Samsung QN900A television.

Since 8K@60 display required HDMI 2.1 compliance, we should be able to conclude that the Intel A750 Limited Edition Graphic card has fully implemented HDMI 2.1.

I heard there are compatability issues with HDMI 2.1 and 8K@60 resolution protocol so perhaps not all 8K@60 products will be compatible with each other. However, I'm delighted that the Arc A750 Limited Edition Graphics card worked with the Samsung QN900A at 8K@60 resolution.

I also found that the ultra high speed HDMI cable is important for getting 8K@60 resolution. Using a slower speed cable will drop my connection to 4K@60 resolution.

[vivekvermae5]

Is your TV getting 4K120Hz 10bit HDR YCBCR 4:4:4 with VRR/ALLM while connected to the HDMI out port of your A750 LE card? can you confirm, please?

[MUC]

Intel Arc Alchemist DG2 currently only features Physical Layers (PHY) for DisplayPort HBR3 (UHBR10 certification still pending VESA CTS Release) or HDMI TMDS (max. 4K @ 60 Hz).

To achieve HDMI 2.1 Fixed Rate Link (FRL), the Protocol Converter (PCON) Realtek RTD2173 is used like shown above.

This makes 4K @ 120 Hz RGB/YCbCr 4:4:4 10 bpc HDR possible on HDMI port site.
ALLM is an HDMI specification that is not available due to the lack of a native FRL PHY. VRR is also an HDMI specification that cannot be provided via (this) PCON. For gaming, you should use a DisplayPort interface and turn on Adaptive Sync to adjust the refresh rate to the game's frame rates. This is of course not possible on a TV (no DisplayPort connector).