CAC-1085 not working with 8K60Hz Sharp TV

3 on 05-01-2021


I bought CAC-1085 from Amazon. I just try to connect it to my graphic card and TV.

Graphic Card: nVIDIA RTX3090 (with latest driver)

TV: Sharp AQUOS 8T-C80AX1 (with latest firmware)

NV [HDMI] to TV [HDMI], It can reach 8K 60Hz and 4K120Hz.

NV [DP] to CAC-1085 to TV [HDMI], It just can do 4K120Hz, CANNOT see 8K60Hz option.


Is there a new firmware for CAC-1085 ?

Thanks for your help.


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1 on 05-01-2021

Hi Kobss,

Can you try the following settings on your PC;

Chroma 420 10bit. This should enable you 8K 60Hz. The bandwidth of DP1.4 is lower than HDMI2.1. I geuss this is the issues. Assuming you are using a certified HDMI2.1 cable no longer than 2 meters with the adapter.

on 13-01-2021

But the CAC-1085 also supports DSC which should effectively double or triple the bandwidth of DisplayPort 1.4.

8K 60Hz is double the pixels of 4K 120Hz per second, so unless the CAC-1085 supports 4K 240Hz, then maybe it should say 8K 30Hz instead of 8K 60Hz? Actually, using CVT-RB timing, 8K 60Hz is 2090 MHz and 4K 240 MHz is 2332 MHz so maybe 4K 217Hz would work (2083 MHz) if 8K 60Hz does. Well, maybe it doesn’t matter since we are talking about HDMI – most HDMI timings use multiples of 297 MHz instead of CVT-RB:

4K30 297 MHz
4K60 594 MHz
4K120, 8K30 1188 MHz
4K240, 8K60 2376 MHz

The RTX and Navi GPUs support DSC (but the CAC-1085 product page doesn’t mention the AMD GPUs, why is that? – maybe it needs to be updated – they can’t update the page every time someone makes a new GPU.

If DSC is not working, 4K 120Hz can be done with DisplayPort 1.4 using 4:2:2.
If HDMI 2.1 is not working, 4K 120 Hz can be done with HDMI 2.0 using 4:2:0.
Same is true for 8K 30Hz. Did you try 8K 30Hz?

NV HDMI is HDMI 2.1. I guess you must have a working HDMI 2.1 cable to get 8K 60Hz.

For NV [DP] DisplayPort 1.4 (HBR3) and DSC need to be working. You’ve updated the Nvidia drivers? You already said you had the latest but doesn’t hurt to double check.

It could be that the cable works with the NV but not the CAC-1085? Not likely but possible.


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0 on 13-01-2021

Also, can you try to downgrade the Nvidia drivers to 456.38? I’ve seen a lot of people having issues getting the right resolutions but when they use earlier drivers it seems to work.

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