Experienced the Pin 20 Display Port Problem

  1. Posts : 983
    Windows 10 Pro

    Experienced the Pin 20 Display Port Problem

    So, my son has the newest and nicest computer in the house. For his birthday, he got enough money to upgrade to a 3rd monitor. He had his primary monitor, a 24" Dell IPS hooked up via Display Port. He has a secondary 24" TN panel hooked up via HDMI.

    The new monitor is a 144Hz monitor, and we picked up the monitor and a display port cable for it. We experienced quite a bit of trouble getting the computer to turn on and boot correctly when the 3rd monitor was attached. It just wouldn't post. The lights would come on, the fans would spin, but the monitors wouldn't come up and the box wouldn't boot. After boot up, we could attach the monitor and it would work, and we could restart and reboot.

    After a fair amount of troubleshooting, I discovered that power was backfeeding into the system from this new monitor over the Display Port cable that we purchased. I found that the LED code screen on his mobo was staying powered up even with the computer disconnected from power. Once I unplugged the monitors display port cable, the light went out.

    Got him a new Display port cable and the problem is gone.
      My ComputerSystem Spec

  2. Posts : 532
    Windows 10

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  3. Faith's Avatar
    Posts : 1,118
    Windows 10 Home May 2019 Update 64-bit

    @pparks1 What is the make and model of the 3rd monitor? And did you use the cable that came with it or a seperate no-name cable? This shouldn't affect cables being used with monitors that has been certified by VESA.

    Recently VESA has experienced quite a few complaints regarding troublesome DisplayPort operation that ended up being caused by improperly made DisplayPort cables. These “bad” DisplayPort cables are generally limited to non-DisplayPort certified cables, or off-brand cables. To further investigate this trend in the DisplayPort cable market, VESA purchased a number of non-certified, off-brand cables and found that an alarmingly high number of these were configured improperly and would likely not support all system configurations. None of these cables would have passed the DisplayPort certification test, moreover some of these cables could potentially damage a PC, laptop, or monitor. We have not seen problems with the cables supplied by major computer brands, or major computer accessory brands, nor have we seen any problems with any of the cables that have been DisplayPort certified.
    How to Choose a DisplayPort Cable, and Not Get a Bad One! - DisplayPort

    Truth be told, I'm not sure how accurate this "20 pin DP issue" really is. 20-pin is actually part of the standard, and most DP cables from reputable brands have 20-pin and it's a non-issue. The answers I get is that you need to have an active power source from an adapter or something, or a bad monitor/GPU/PSU, for it to be an issue. The GPU should not be accepting power on it either. 20-pin is there as an optional passive wire, or it's isolated and cannot be used. Either way, the DP cable coming with a purchase of the monitor from a known brand should not give issues in this way.
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  4. Posts : 983
    Windows 10 Pro
    Thread Starter

    The monitor is an AOC
    AOC G2590FX 24.5" Full HD 144Hz VGA - Micro Center

    The monitor did not come with a cable, so I just bought one while at Microcenter.QVS DisplayPort Male to DisplayPort Male - Micro Center

    Replaced the above cable with the following cable.https://www.bestbuy.com/site/insigni...?skuId=5580672

    After replacing the cable, we have experienced 0 problems.

    There was power coming back over that cable, no question about it. The LED stayed lit on the motherboard with the power disconnected from the Power supply. The lights went out as soon as I disconnected the display port cable.
      My ComputerSystem Spec

  5. Faith's Avatar
    Posts : 1,118
    Windows 10 Home May 2019 Update 64-bit

    QVS has not been certified by VESA, nor do I find them in their database. That Insignia cable has though (NS-PDD607). Before buying a DP cable just make sure the cable is certified, or use a cable that came with the monitor on a reputable brand and you should be fine. I'm glad you got it sorted. Not sure about legality of those QVS cables either, because as far as I know, in order to get the DP logo on the cables they have to be certified. Since I didn't find "QVS" in their database even, and they have the logo on it, it confuses the heck out of me.
      My ComputerSystem Spec


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