PC Building

[Haltesh]

TLDR: New PC, Ryzen 8700g/ASRock B650M Pro RS, no video signal on two seperate DP1.2 4k60hz monitors from different manufacturers. Both 4k60hz and 1440p165hz modes are confirmed to work on a DisplayPort 1.4 monitor. Looking for other people with similar hardware to see if I should try RMA-ing either the CPU or the motherboard.

Hello everyone,

I just purchased a new PC with a Ryzen 8700g on an ASRock B650M Pro RS motherboard, intending to use it with my old Dell 2715q 27 inch 4k monitor. This is an older monitor I purchased back in 2016, before DisplayPort 1.4 was widely used, so it only supports DisplayPort 1.2, and maxes out at 4k60hz.

The motherboard specs list compatibility for up to 4k120hz via DisplayPort 1.4, and my understanding was that DisplayPort is backwards compatible, so I figured I was good to go.

When I tried to boot the system for the first time, the keyboard and the mouse lighted up, but I had no signal on the monitor. None of the debug LED indicators were lit, so I figured the system booted into BIOS, but I could not be sure. So I shut the PC down and plugged in a newer monitor (MSI MAG274QRF-QD, a 1440p165hz DisplayPort 1.4 model), started back up and now had a working display. To rule out Dell as the culprit, I tried my brother's Samsung U32H850UMU, which is a slightly newer (2017) 32 inch 4k60hz DisplayPort 1.2 monitor, and just like with the Dell, I have no signal.

I've setup my system using the 1440p monitor, and confirmed the monitor works at 165hz (it was locked to 60 in the bios) and also that it works at 4k60 (the MSI MAG274QRF-QD accepts a 4k signal for compatibility with the PS5).

I am honestly very surprised by this experience. I've used this monitor with multiple GPUs over the years, ranging from discrete offerings from both nvidia and AMD, to integrated Intel graphics, and it has always worked. It never even occurred to me that this was something that could even happen, at worst I figured the display could not work at it's max resolution and/or refresh rate.

Is anyone successfully using a similar monitor with their Zen4 integrated graphics? Is the hardware simply incompatible, or is the CPU or motherboard defective?

[BigAl01]

I believe that Display Port 1.4 is backwards compatible with Display Port 1.2; The cable rated for DP 1.4 can handle the higher bandwidth, while the cable rated for DP 1.2 will have problems with 4K monitors above 60 Hz due to bandwidth limitations.  The problems you have might be related to a motherboard BIOS issue, so I would look for a BIOS update to see if that allows the use of the older 4K monitors at 60 Hz.

[Haltesh · Accepted solution]

Well, after some additional testing and some back-and-forth with ASrock support, I managed to at least get the monitor into a mostly-working state.

It simply does not work in BIOS, at least not consistently. Sometimes it does even work in BIOS when I reboot my PC, if the display does not go to sleep too fast. In the OS, it works with no problems on a clean boot; A reboot may cause it not to work momentarily, but just toggling inputs or turning the monitor on and off again will make it work immediately.

I also have to give a shout out to ASrock support, as they almost immediately responded with their own test results with a DisplayPort 1.2 monitor they had available in their lab, and two or so days later later actually sourced a Dell 2718q (which I believe is the direct successor to my own monitor, and also limited to DP1.2) for testing. Their configuration worked in BIOS with no problems, so either my monitors, being older, have a subtle bug in their DisplayPort implementation, or there is another difference that I'm unaware of.

Either way, since the display works outside of BIOS, and any future monitor I get will be DP1.4 or later anyway, I've decided not to bother with an RMA.