Spectrum DP 1.4 can't go beyond 60Hz (AMD w/o DSC), feedback welcome

I found out we have a main thread for this topic;

survey answers are still always welcome

So, Spectrum is here, something we’ve all been waiting for. Since I haven’t gotten around to buying a new GPU yet, I’m still using my AMD Vega 56 and connect it to the Spectrum via DisplayPort 1.4, which should still give me 4k120 without using DSC.
The problem is Spectrum will not go beyond 60Hz on all resolutions except 1080p. The option does not even show in Windows and takes no effect under Linux (DE: Plasma) I have updated the firmware to 104, tried three separate DP cables, two of which were new bought 1.4’s and brought down color depth to 6b, but it doesnt change anything. A check in the AMD panel shows that the link speed is able to reach 32Gbit on 8b or 10b color depth.
I found this thread describing the exact same problem, however it was declared resolved on the notion that without DSC, you wont be able to hit 4k144. That does not however address the actual problem.

Now I’ve read people use Spectrum successfully with DP, so I want to find out what the actual problem is, and maybe @Lore_Wonder can help with this as well. My current suspicion is, that there are certain modes set for HDMI 2.1 and DP 1.4 with DSC, but without DSC there are modes disabled which wouldn’t have to be. While I consider myself tech savvy, I do not know what exactly enables or disables modes, if they are at all.
When I say modes, I mean Resolution/Refresh Rate combinations.
The only other Problem I can think of would be an AMD Driver Problem.

Enough of my rambling though, please give me your feedback

Can you run Spectrum with at least 4k120?

  • Yes, I use HDMI 2.1
  • Yes, I use DP 1.4 with AMD RX5000 (RDNA) or newer (w/ DSC)
  • Yes, I use DP with Nvidia RTX 2000/GTX 1600 or newer (w/ DSC)
  • Yes, I use DP with AMD RX Vega (Desktop), Rx 500(GCN) or older (w/o DSC)
  • Yes, I use DP with Nvidia 1000 (Pascal) or older (w/o DSC)
  • No, I use DP 1.4 with AMD RX5000 (RDNA) or newer (DSC)
  • No, I use DP with Nvidia RTX 2000/GTX 1600 or newer (w/ DSC)
  • No, I use DP with AMD RX Vega (Desktop), Rx 500(GCN) or older (w/o DSC)
  • No, I use DP with Nvidia 1000 (Pascal) or older (w/o DSC)
  • No, but I use HDMI 2.0 or older
  • No, but I use DP 1.2 or older

0 voters

The Vega line doesn’t have DSC.

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Yes, I’m aware and I’ve mentioned it in the survey and the second sentence.
Sorry if it’s hard to read, I sometimes have trouble sorting my thoughts well.
What I’m getting at however, is that without DSC I should be able to still get to 4k @120 Hz according to this list.

But I don’t.
So I’m not sure if the fault lies with the GPU driver, some setup, the monitors hardware, firmware or something entirely else.

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So before i had the spectrum my Radeon VII was hooked to a Acer ConceptD CP3271KP and it could maintain a refresh rate from 144Hz but only when connected via TWO Displayport Cables.

My radeon software also shows that AMD FreeSync is not supported???

Unfortunately it seems unpossible to get over 60Hz at this point.


As of now i tested with an HDMI 2.1 Cable from Stouchi (8K Ultra HD 48Gbps High Speed 8K60 4K120 144Hz eARC HDR10 4:4:4 HDCP 2.2&2.3)

a CableDeconn DisplayPort 1.4 to HDMI 2.1 8K Cable Converter 8K@30Hz 4K@120Hz Direction Compatible with DisplayPort PC and HDMI Displays

and a 8K capable DisplayPort Cable

Could someone from the Eve Team consider the two cable solution? @MarvyMarvz @Lore_Wonder

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Spectrum only has one DP port, so a two cable solution strikes me as impossible.
Regarding the FreeSync support: I had the same thing, but could fix it by turning it of and on again at Spectrums Menu.

Also, there is another thread regarding this threads problem as well:

I’m keeping this one open for the sake of the survey, but I think future posts are better written there.

I know that, but maybe it is possible with two displayport to hdmi cables?

The radeon vii has 3x dp ports and 1x hdmi.

which option in the spectrums menu needed to be turned off and on?

the Adaptive Sync option under Performance

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I looked into this for several hours and unfortunately I’m confident that there is no way to push 4k120Hz from a Vega 56 or 64 card. While they do have DisplayPort 1.4, they don’t implement DSC. Even with chroma subsampling turned on, the option to go beyond 60Hz simply wasn’t there.

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Please post on and read the mentioned main thread. As I wrote there, I was able to achieve 4k120 on linux.
It does not make sense however to post simultaniously on 2 or 3 threads discussing the same problem.

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I did come to somewhat of a resolution using my RX580 without DSC. Haven’t been here in a while, sorry. I can run Spectrum at 4k 4:4:4 @ 105hz using a custom resolution. Anything higher than that fails. I also cannot run at 10bpc, only 8bpc. It doesn’t really answer the issue, since the bandwidth of DP1.4 alone should be enough to run it at 4K120hz, but it CAN run at higher than 60hz @ 4k.

Freesync is on.

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