CAC-1080 AMD 290x unable to output 4K 60hz

Hi JayZing,

What TV do you use? Model and modelnumber.

The AMD r9 290x has only DP1.2. The CAC-1080 is fpr DP1.4. Maybe try the CAC-1070? Is your HDMI cable 2.0?

My TV is a Hitachi 55C60. 

Is there a way to tell what version a HDMI cable is? Various sources I’ve came across, stated that the HDMI revision is with the connectors themselves. I do remember that the hdmi cable I have was bought in 2014. There is no model or specs written on them.  

The CSC-1080 is backwards compatible. I got 4k 60hz working by downgrading drivers to 16.8.3. Other sources suggest 19.9.2 may work as well. 

Thanks for assisting. Perhaps this information needs to be stickied for anyone else that uses AMD gpus with this adapter.  

The CAC-1080 uses four lanes of HBR2 to do 4K 60Hz. DisplayPort 1.2 supports HBR2.

DisplayPort 1.4 is required for HDR (but macOS can do HDR from DisplayPort 1.2 with some adapters? I can’t get HDR with Club-3D’s adapters from macOS whether I’m using DisplayPort 1.2 or 1.4)

DisplayPort 1.4 is required for 4:2:0 pass through.

DisplayPort 1.2 can do 4:2:2 pass through but not 4:2:0. But the adapter can do conversion from RGB to 4:2:0 so that shouldn’t matter if you need 4:2:0.

The CAC-1080 has this “In addition HDR with deep color up to 12Bpc at 4K 60Hz is supported through the conversion of RGB/YCbCr 4:2:2 over DP link to YCbCr 4:2:0 on the HDMI™ output with a horizontal expansion to CEA timings.” I don’t understand “horizontal expansion to CEA timings”. I understand that a timing involves a pixel clock, horizontal pixels, vertical pixels, horizontal blanking pixels, and vertical blanking pixels. Horizontal expansion seems (I am guessing) to mean that the pixel clock is increased to have more total horizontal pixels per line (the number of horizontal blanking pixels must be increased so that the horizontal scan rate remains the same). It would be nice to have some example numbers to explain what it’s doing. This horizontal expansion may cause a couple issues:

1) horizontal expansion may require a scan line buffer which may be limited to a certain number of pixels, so for example, maybe it can’t do more than 4096 pixels wide for wide screen displays (the product page says 4096 is the max so maybe this is why).

2) If it’s changing pixel clock for horizontal expansion, how does it decide when to do that? What if I want to do some arbitrary timing? How will it choose when to change my timing?

I may be totally wrong here. The other part of the context for horizontal expansion is the conversion from 4:2:2 to 4:2:0. But that is just removing chroma from every second line or averaging chroma between every two scan lines – I don’t see how “horizontal expansion” describes that are why it’s needed.

Reading the features section, it says “Horizontal expansion of Vesa CVT to CEA Timings (as per DP 1.4 spec)”. The DisplayPort 1.4 spec isn’t available online so I guess I’ll never know what this means. CVT timings (replaces GTF timings) are usually used by CRTs.