Hello. I have been using CRU on many different systems through the years but currently i have one issue i cannot explain.
My system at the moment has an AMD 6900xt and 2 identical LG 27GL850 (1440p@144hz@10bit) of the latest revision (original revision was supposedly DP 1.4 but couldn't do HBR3, instead it had reduced timings from the factory to be able to just squeeze the signal into HBR2. But it was advertised as DP 1.4 and even had this option in the monitor menu but you could see 4x5.4Gbps link was the max. Not even reviewers caught this and there is no official revision in the model number anywhere, the revisions were found by the community. Liar LG)
Software wise i am running W10 22H2 with MPO disabled (as it causes problems like driver timeout crashes, issues in browsers etc, it's known windows issue and even nvidia posted reg edit to disable it as temp fix) and the latest 22.11.1 drivers that supposedly fixed the high Vram clock issue (yet again) - it doesn't, with my monitors i need to drop both to 60hz in order for it to downclock, even increasing vertical blanking doesn't fix it. Running single monitor if i remember in much older drivers it could downclock at 120hz but not at 144hz.
Or reddit in this driver release an AMD rep said this:
"It's ultimately contingent on graphics and display hardware. This isn't something that could be influenced by driver software (otherwise it would have been done already).
VBI on the other hand can be influenced by custom resolutions in Adrenalin, though that's pretty advanced and I don't generally like to recommend this."
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.
edit: He also said this which confirms the above: "There are two key aspects to low idle mclk with multiple displays. Total display bandwidth and vertical blanking interval."
Anyways, i've decided to try overclocking one of my 27GL850 monitors as i know there are 165hz versions with the same panel and possibly TCON, and LG just put a software limit. It's pretty apparent because even at 155hz it works but displays an annoying out of range overlay dialog you can't disable. But anything lower and it doesn't do it.
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).
Here are some screenshots (here 148hz because i was trying to see if it happens at different refresh rates too):
Running with overclock HBR3 no issues:
https://i.imgur.com/Y7Gb5CO.png
Running with overclock after it locks into 6bit HBR2:
https://i.imgur.com/oIkSDSu.png
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??)
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)
