Custom Resolution Utility (CRU)

[ToastyX]

(12-01-2022 08:15 AM)TnF Wrote:  But i know this is BS because there seems to be a limit where if the total pixel clock exceeds a specific value, vram clocks will switch to high because there is no other intermediary powerplay clock state to support that total bandwidth..It's 2022 and multimonitor high resolution/bandwidth users still get f*cked over with this. Nvidia does it too. They will never learn it looks like it.

The memory clock issue has nothing to do with bandwidth. Changing the memory clock while the screen is refreshing will corrupt the image while the memory is being retrained, so the memory clock needs to change during the vertical blanking period to avoid this. If the vertical blanking period is not long enough, there won't be enough time to finish retraining the memory before the next refresh starts. That's why the memory clock won't change if the vertical blanking is too low. That's for a single monitor. For memory clock changes to work with multiple monitors, both monitors must be perfectly synchronized so the vertical blanking period happens at the same time, otherwise there's no way to avoid corrupting the image on one of the monitors. You have to make sure that the timing parameters for the detailed resolutions for both monitors match exactly. If they do match and it still won't clock down, then that's a driver bug or hardware-specific limitation. There should be no issues with clocking down with two identical monitors at 2560x1440 @ 144 Hz if the vertical blanking is long enough. What happens if you try 8 bpc color instead of 10 bpc?

(12-01-2022 08:15 AM)TnF Wrote:  The issue i am having is that while at factory timings 1440p@144hz@10bit both monitors will run HBR3 (4x8.1Gbps) all day, everyday at all scenarios, anything i've tried over that it will work but when the monitor is turned off (like windows display sleep timeout) and then you wake it up that will force DP link re-training, it will run into some kind of safe mode where it drops down bitrate to 6bit and HBR2 even though it just did work just fine before. I can see that quite easily because any color gradient shows visible banding.

When this happens in the radeon settings it will make bit depth option disappear, and windows resolution information in settings will still show 10bit when it's clearly not. To recover from here i need to drop to 120hz (which is one of the standard monitor modes, not a custom one) change bit depth to 8bit, then switch back to my overclocked setting and re-set to 10bit and it will stay at HBR3 until DP link retraining is initiated again. This method works 100% consistently but i could also just switch to 120hz and back without changing bit depth but this doesn't have 100% success.

I've tried different timings but i couldn't find any settings that will prevent this from happening. Also changing the "Voltage swing" and "PreEmphasis" overrides didn't make any difference. However i've noticed a couple of other weird things. First i get a 3rd entry of this monitor in CRU with the factory edid conf that is never active, and when it swiches to HBR2 6bit from HBR3 10bit the actual refresh rate changes (example from 150hz to 149.9xxxhz)

My guess this happens because it tries to do some kind of quick DP link re-training and it fails, so it switches to HBR2, but since it can't do that refresh rate at that resolution it reduces bitrate to minimum and re-tries (since it should be possible to run it at 8bit, but it skips that entirely).

If the EDID actually changes when this happens, then this is something the monitor is doing, not the GPU. My guess is the monitor might have a firmware bug that causes it to be in HBR2 mode (1.4 disabled) when waking up from sleep. DisplayPort automatically downgrades the color depth if there's not enough bandwidth.

(12-01-2022 08:15 AM)TnF Wrote:  Running stock settings HBR3 144hz: https://i.imgur.com/N5VLZkL.png
Some reference timings at 150hz: https://i.imgur.com/smJskaU.png (weirdly here it says CVT timings will fit into HBR3 but CRU locks you well before that, why??)

Vertical front porch can't be higher than 63 for EDID detailed resolutions, and the pixel clock can't be higher than 655.35 MHz. You can use a DisplayID extension block to add detailed resolutions with higher limits.

(12-01-2022 08:15 AM)TnF Wrote:  Also i have one more general question..when overclocking a freesync monitor you need to increase the freesync range in order for it to work up to the new overclocked refresh rate or not? Also. does the pixel clock limit you can edit there play any role? (i did increase those in my case if it's relevant)

You need to increase the range if you want FreeSync to work at the higher refresh rate. Some monitors handle higher refresh rates differently with FreeSync than without, like frame skipping if the refresh rate is not within the range. The pixel clock limit doesn't affect FreeSync, but AMD's driver will ignore any resolutions higher than the limit, so you should increase it if you're adding a detailed resolution with a higher pixel clock. The pixel clock value must be a multiple of 10, and the HBR3 limit is 1080 MHz, so you can just use that.