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DisplayPort Cable Providing Power To PC

Last response: in Systems
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August 29, 2010 8:00:43 PM

I just built a new machine with an ATI Radeon 5850, a Gigabyte GA-X58A-UD3R motherboard, and a displayport monitor (Dell U2311H) which is connected via a displayport cable.

The problem I have is that when I switch off the computer, the system is still receiving a small amount of power through the displayport cable.

I have verified this by disconnecting all the cables from the computer (including the PSU cable) except for the displayport cable, and the keyboard lights are still on, as is a fan control unit, and various lights on the motherboard. As soon as I take the displayport cable out, all the lights go out, and go back on again when I plug the displayport cable back in.

If I connect the same monitor via a DVI cable this does not happen.

Unfortunately I don't have another displayport cable or displayport capable monitor to try to isolate the problem further.

Does anyone have any suggestions as to why this is happening?

Thanks
January 17, 2011 3:34:38 AM

sschilachi said:
I just built a new machine with an ATI Radeon 5850, a Gigabyte GA-X58A-UD3R motherboard, and a displayport monitor (Dell U2311H) which is connected via a displayport cable.

The problem I have is that when I switch off the computer, the system is still receiving a small amount of power through the displayport cable.

I have verified this by disconnecting all the cables from the computer (including the PSU cable) except for the displayport cable, and the keyboard lights are still on, as is a fan control unit, and various lights on the motherboard. As soon as I take the displayport cable out, all the lights go out, and go back on again when I plug the displayport cable back in.

If I connect the same monitor via a DVI cable this does not happen.

Unfortunately I don't have another displayport cable or displayport capable monitor to try to isolate the problem further.

Does anyone have any suggestions as to why this is happening?

Thanks


OMG... I have the same problem. I have two Dell U2311H and when I turn off my computer and even unplug the computer, parts of my computer remains slightly lit like my fan LEDs. Sooo bizarre... I have two 6850s in CF and a Biostar T5XE Motherboard.
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January 21, 2011 5:30:09 PM

That's pretty weird, maybe it's something to do with the monitor then. I still haven't figured out the problem - if you do please let me know, it would be a life saver as I have a fan control unit with an alarm, which receives power when switched off, but obviously the fan isn't spinning so the alarm sounds as it thinks the fan is broken!
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Best solution

February 24, 2011 11:29:34 AM

sschilachi said:
Does anyone have any suggestions as to why this is happening?


Your Displayport cable does not live up to the specs. I have a Gigabyte ATI HD 5770 and a Dell U2311 and I had the same problem. The Dell powered my pc when both where turned off. The problem is that a Displayport cable between graphics card and monitor is not supposed to connect pin 20 (power). I solved my problem with a new cable (an HDMI -> DP cable).

From http://www.displayport.org/consumer/?q=content/faq
Quote:
Q: Why isn’t there a wire on pin 20 (POWER) on the standard external DisplayPort cables?
A: The reason power isn't included in standard cables is because both source and sink devices are designed to provide power. Captive, attached cables often include the power wire. If it is desired, for example, that a particular source device utilize the power available from the mating sink device, then that Source device could include an attached or dedicated cable that carries the DisplayPort power signal. Same could be applied to a sink device.


Cheers...
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March 6, 2011 8:48:09 AM

Thanks, that was exactly it! I managed to just take out the pin 20 wire from the cable (Not recommended - I almost broke the connector and had to somewhat force it into the monitor to fit!)

So yea, I can confirm that the cable was the problem, as that completely resolved the issue.

Cheers!
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March 6, 2011 8:48:20 AM

Best answer selected by sschilachi.
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March 6, 2011 6:35:04 PM

I'm glad you fixed the problem :-) I'm curious as to how many people experience this kind of problem. For me the cable was the last thing I suspected. And what cables do live up to the specs? My defect cable is a Deltaco DP-1020.
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March 23, 2011 1:00:05 PM

soelv said:
Your Displayport cable does not live up to the specs. I have a Gigabyte ATI HD 5770 and a Dell U2311 and I had the same problem. The Dell powered my pc when both where turned off. The problem is that a Displayport cable between graphics card and monitor is not supposed to connect pin 20 (power). I solved my problem with a new cable (an HDMI -> DP cable).

From http://www.displayport.org/consumer/?q=content/faq
Quote:
Q: Why isn’t there a wire on pin 20 (POWER) on the standard external DisplayPort cables?
A: The reason power isn't included in standard cables is because both source and sink devices are designed to provide power. Captive, attached cables often include the power wire. If it is desired, for example, that a particular source device utilize the power available from the mating sink device, then that Source device could include an attached or dedicated cable that carries the DisplayPort power signal. Same could be applied to a sink device.


Cheers...


may i know which brand hdmi--->dp cable u bought. branded or local. could u please send me the link of the cable u have purchased. coz, me also bought one hdmi--->dp cable. but, it's not working for me. my motherboard(asrock 890gx extreme3)hdmi to dell u2311h displayport.
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September 2, 2011 8:45:39 AM

I'm also looking for new cables to solve this issue. The ones I have are no good. Does anyone have any recommendations?

I need mini displayport to displayport or DVI.

Thanks
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March 20, 2013 10:30:26 AM

soelv said:
sschilachi said:
Does anyone have any suggestions as to why this is happening?


Your Displayport cable does not live up to the specs. I have a Gigabyte ATI HD 5770 and a Dell U2311 and I had the same problem. The Dell powered my pc when both where turned off. The problem is that a Displayport cable between graphics card and monitor is not supposed to connect pin 20 (power). I solved my problem with a new cable (an HDMI -> DP cable).

From http://www.displayport.org/consumer/?q=content/faq
Quote:
Q: Why isn’t there a wire on pin 20 (POWER) on the standard external DisplayPort cables?
A: The reason power isn't included in standard cables is because both source and sink devices are designed to provide power. Captive, attached cables often include the power wire. If it is desired, for example, that a particular source device utilize the power available from the mating sink device, then that Source device could include an attached or dedicated cable that carries the DisplayPort power signal. Same could be applied to a sink device.


Cheers...


Althouth this is an old thread, I'm saying my opinion. I've got the same screen with an AMD Radeon HD 7870. My psu which is a Tt 775w makes a tik tik noise for a few minutes then it stops and you can barely hear the fan turning

Putting an HDMI to DisplayPort cable isn't the solution ..this is a workaround. We need a proper cable? who knows, maybe it was a bad design from Dell? ..I'm out of clues

EDIT: The noise stopped when I configurate the screen from auto to displayport cable(OSD settings) but the PSU fan is still working :( 
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