Display – Why 75Hz Monitor Shows Only 29Hz Refresh Rate

displayrefresh-ratewidescreen

I recently purchased a new Viewsonic VA3456-MHDJ Ultrawide WQHD 34-inch IPS 75Hz monitor, but when I connect it to my computer, it only shows a refresh rate of 29Hz in the display settings. I'm running Windows 10 and have updated my graphics card drivers, but the problem persists.

advanced display settings
I have tried changing the refresh rate from the advanced display settings, but it doesn't allow me to select anything other than 29Hz, as shown in the attached screenshot.

I've tried using different cables and ports, but it doesn't seem to make a difference. I've also checked the monitor's settings, but I can't find any options to adjust the refresh rate.

Do you think this is a defect on the monitor or is there a way to fix this issue through software or settings?

Best Answer

Often these limitations are due to bandwidth limitations. E.g. 3440x1440 at 60Hz requires 7.51 Gbps (perhaps your monitor does not support that mode), and 3440x1440 at 75Hz requires 9.45 Gbps.

Different connection types have different limits:

  • HDMI 1.4: 8.16 Gbps -- too low for 3440x1440 @75Hz
  • HDMI 2.0: 14.4 Gbps
  • HDMI 2.1: 41.9 Gbps
  • DVI: 3.96 Gbps
  • DVI Dual Link: 7.92 Gbps
  • DisplayPort 1.0: 8.64 Gbps
  • DisplayPort 1.2: 17.28 (newer versions have even more)

Please also check that if you are using HDMI you are using a HDMI 2.0 or greater cable. These cables are typically marked "Premium High Speed HDMI Cable" or "Premium High Speed HDMI Cable with Ethernet".

You also need to check that any cables, dongles or adapters you are using are also rated to the required standard.

For more info, you may like to see LinusTechTips display bandwidth calculator page.

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