Enabling 144hz for Asus PG278Q on AMD gpu

[erssn]

Hello @ToastyX and all!

I have been lurking the forums for a while, trying to solve this problem with my Asus pg278q 1440p 144hz gSync v1 monitor.

The main problem is that back in the day, AMD 290/290x didn't work well with the standard timings of the monitor and AMD restriced the timings in the driver, basically prohibiting the use of 144hz with this monitor if using an AMD gpu. The monitor now just supports 120hz with AMD out of the box.

I found a smart kiddo on the Asus forums managed to find new timings that worked both with the GPUs and the monitor. See here: Asus ROG forums. I tried this solution with my Vega 64 and it worked beautifully!! Now, 7-8 months later I'm sitting here with my new RX 5700 XT and I can't f*cking get it to work whatever settings a enter into CRU. If a use the timings from the Asus thread, the 144hz option does not even show up in windows, however with "LCD Native" settings in CRU or with just an incremental increase to vertical blanking it shows up as an alternative. However, the monitor then gives "Out of range" when enabling 144hz.

Another guy seems to have hade the same issue as me in the CRU thread. See here: CRU Thread post 5119. ToastyXs answer is that probably AMD started restricting low Horizontal Blanking values to get rid of the problem with 290/290x. Reasonable. Soon thereafter I believe ToastyX added "HBlankingLimit remove" to the ATI/AMD Pixel Clock Patcher tool, since its states "HBlankingLimit 56" which is the same limit as post 5119 is referring to. I still have this issue, even though applying the pixel patch.

However: I believe now that there is a Vertical Blanking Limit apperant based on the many problems people are having with high memory clock speeds on RX 5700/RX 5700XT with 144hz. See here: Reddit thread. The main issue with the high memory frequency is low Vertical Blanking, = AMD restricts the driver from working with low vertical blanking, and therefore the compatibility between RX 5700XT and PG278Q 144hz?


TLDR: The Asus Rog forum custom resolution fix was working with my Vega 64. After switching to RX 5700XT i cannot use 144 hz with PG278Q anymore. Is there maybe a new V.Blanking limit in the driver? Is it possible to update/edit the pixel patcher tool to remove it, or regedit?

I did my research but now I'm stuck. Does anyone have any input how I can move forward? I really want 144 hz instead of 120 without buying nvidia or a new monitor (love it). (I have a new 1.4 DP cable since 2 days ago, same issue).

Pls help /erssn

[ToastyX]

The problem is AMD doesn't allow horizontal blanking less than 56 because it breaks their HDCP implementation with newer cards, and the monitor won't accept horizontal blanking greater than 40, so there's no way to make this combination work without disabling HDCP and modifying the driver. AMD puts the blame on the monitor for not supporting standard timing parameters.

The memory clock issue with low vertical blanking has nothing to do with your problem. The memory clock can't change if the vertical blanking is too low because there won't be enough time to retrain the memory without corrupting the screen contents. What is the lowest vertical blanking that the driver will accept with your RX 5700XT?

[erssn]

(02-09-2021 09:15 PM)ToastyX Wrote:  The problem is AMD doesn't allow horizontal blanking less than 56 because it breaks their HDCP implementation with newer cards, and the monitor won't accept horizontal blanking greater than 40, so there's no way to make this combination work without disabling HDCP and modifying the driver. AMD puts the blame on the monitor for not supporting standard timing parameters.

The memory clock issue with low vertical blanking has nothing to do with your problem. The memory clock can't change if the vertical blanking is too low because there won't be enough time to retrain the memory without corrupting the screen contents. What is the lowest vertical blanking that the driver will accept with your RX 5700XT?

Hmm. It's very weird because i don't seem to have any issues with the horizontal timings. The 144hz option appears in the windows 10 menu when running the horizontal timings from the Asus forum post (8/16/16) and atleast 10 vertical blanking (e.g, 1/1/8 or similar). That's why i feel like there is some other issue than the 40/56 horizontal blanking.

Do you have any ideas of what i could test? As i mentioned i did not have any issue with my vega 64 and the custom timings. I'm very thankful for your help!

[ToastyX]

Is 10 vertical blanking the lowest the driver will accept?

[erssn]

(02-09-2021 10:10 PM)ToastyX Wrote:  Is 10 vertical blanking the lowest the driver will accept?

Yes, I tried a few different vertical combinations and yes. At 1/1/7 or for example 3/3/3 the 144 options is rejected. At 1/1/8 or 1/2/7 it is available but results in out of range. So yes, 10 seems to be the lowest the driver is accepting. (if it is the driver and not some other weird issue)

[ToastyX]

That does seem like a new limit, but finding it would be hard because the number 10 exists in hundreds of places in the driver. The limit seems to be 9 on my Vega 8 laptop, so the limit is GPU-specific, which means I have no way of figuring out where the limit is for the RX 5700XT. Even if I found it, there has to be a reason they're limiting it, so changing it might not even work.

[erssn]

(02-10-2021 01:56 AM)ToastyX Wrote:  That does seem like a new limit, but finding it would be hard because the number 10 exists in hundreds of places in the driver. The limit seems to be 9 on my Vega 8 laptop, so the limit is GPU-specific, which means I have no way of figuring out where the limit is for the RX 5700XT. Even if I found it, there has to be a reason they're limiting it, so changing it might not even work.

I see, so maybe the limit was 9 on my Vega 64 also then because of similar architecture. Hence, why 1/1/7 worked.

I understand, and I'm thankful for looking at my issue anyway. Would it make sense that is has to do with the memory idle frequencies? What I think is weird is that i never encountered the 56 H.blanking limit, neither with with my Vega 64 nor the RX 5700XT...

[ToastyX]

(02-10-2021 09:58 AM)erssn Wrote:  Would it make sense that is has to do with the memory idle frequencies?

No, it has nothing to do with that. There's probably a minimum amount of blanking that the GPU can handle. For older cards, it was 5, and the driver didn't restrict lower values, but it wouldn't display anything below 5.