Need DisplayLink Advice - 35Ft. DisplayPort Cable
 

Hello,

I work customer support for a Display manufacturer and have a customer experiencing issues using my Display product and the Dell 3100 Dock with the USB to DisplayPort adapter built in.

We recommend using no more than a 7m(23ft.) cable to our customers, however they are using a 10.6m(35ft). cable between the devices and are seeing artifacts when playing video.

I highly suspect they are using a cable that is simply too long, but rather then just dropping the signal I think we are in the grey area where we see enough signal degradation to cause video issues, but not enough to cause the video to actually drop.

I I have not been able to find any literature that calls out maximum cable lengths, but I'm looking to justify to the customer why they need a proper powered extender here, and if you cab share any advice that would be helpful.

Thanks!

Hello,

What kind of resolution are they trying to achieve?
What are the characteristics (which speed is guaranteed) of the long cable causing issues?

The technical objectives of DisplayPort 1.2 were defined under the specification chapter 1.2.1. Among others:
- Support full bandwidth transmission via direct drive over a two meter cable.
- Support reduced bandwidth transmission via direct drive over a 15 meter cable. DisplayPort supports a minimum of 1080p lines at 24bpp, 50/60Hz over 4 lanes at 15 meters.

Then, depending on the bandwidth the cable can support (due to its electrical characteristics), you would have different resolution limits achievable in real applications.

DisplayPort compliance is tested with new releases to ensure no firmware or host software change degrades the end product behaviour over time. The release notes indicates what compliance can be passed with which DisplayLink chip on which standards.

Kind regards,
Alban