I am looking for assistance to resolve an intermittent failure with my P2715Q operating at 3840x2160 60Hz. While I describe the problem as intermittent, know that I can operate in this mode only about 25% of the time. I have reliable operation operating at 3840x2160 30Hz, but I would like to have reliable operation at 60Hz refresh. I am using the Displayport interface between my laptop and the monitor.
The issue appears to be one of initial synchronization between my laptop computer and the display. If I have correct display output when I switch on the monitor (or wake my laptop from sleep, start my laptop, plug in the monitor cable, etc.), then the monitor operates as expected without issue until the next start up event (such as wake from sleep, etc.). If the initial synchronization fails, then the monitor displays the message "The current input timing is not supported by the monitor display. Please change your input timing to 3840x2160, 60Hz or any other monitor listed timing as per the monitor specifications." I can at this point power cycle the monitor repeatedly until the initial synchronization is successful and have correct operation. It is not unusual to power cycle the monitor one to five times to achieve correct operation at 60Hz refresh.
If I set Displayport MST to 'Secondary', the monitor operates at 30Hz refresh and is fully reliable on every initial start up.
I am using up to date graphics drivers and P2715Q monitor drivers. Speculating a marginal electrical issue, I have tried two different cables between my laptop and the monitor with indistinguishable behavior.
The diagnostic information available from Dell (I have read the related Knowledge Base article SLN296015 related to this behavior) suggests my graphics card and/or laptop does not support DP1.2 and is instead supporting DP1.1. However, Asus and nVidia documentation assert that DP1.2 is fully supported on the USB-C Thunderbolt 3 port used to connect my lap top to the monitor. It is not clear to me if a DP1.1 system could exhibit the observed intermittent success at 60Hz. As noted previously, if the initial synchronization is successful, the monitor functions without issue until a subsequent sleep/wake up cycle. I am operating the monitor at 3840x2160 60Hz as I type this post.
Here is some additional system details to sharpen a response:
- 20 digit alpha-numeric monitor serial number: CN-0X24K1-74445-65P-AF5L A03
- Specific computer model: Asus ZenBook UX501VW
- Operating system: Windows 10
- Video card: nVidia GeForce GTX 960M with 2G GDDR5 VRAM
- Video card driver version: Version 368.81 released 2016-Jul-14
- Video out ports are available on the video card: Thunderbolt 3 (USB-C) and HDMI 2.0
- Video out port in use from video card: Thunderbolt 3 (USB-C)
- Video in port in use on the monitor: Displayport
- Cable in use to attach the video card to the monitor: Two Cables have been used with indistinguishable results. Pluggable 1.8 meter USB-C to Displayport and Accell 1.8 meter USB-C to Displayport
- Windows power plan: Windows 10 Balanced power plan
- Monitor resolution indicated by monitor: 3840x2160, 30 Hz Maximum: 3840x2160, 60Hz
- From who was the monitor purchased? Monitor was purchased from Dell
Thank you for any assistance you can provide.