Video Display and Multiple Video Display General Information

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Frequently Asked Questions

• Question: My Video Card has a Dual-Link DVI port on it. Why I cannot get the max resolution supported my display.
  Answer: Each DVI port will only provide video for a single display. When using Digital Video Interface (DVI) video, most displays have a standard "Single Link" connection. Most video displays do not require any extra video signal from the system to show video. Some displays are larger and require a boost to the signal coming into the display. Many 30", some 29" and 27" displays will have a "Dual Link" DVI connection to allow large screen display resolutions of 2560x1600 by interlacing the signals. This does not look any different from any other DVI connection. You cannot use the display at the full screen resolution if they are not using a "Dual Link" hardware configuration.
  
  To have a "Dual Link" set up, you need three things. A display with "Dual Link" connection. A Dual Link DVI cable that is identifiable by having 24 pins for connecting the 18 pins in a "Single Link" DVI cable. A video card that has "Dual Link" DVI output (2560x1600). Once that is connected, the display can use any screen resolution that it can handle. Any cable adapter that is used must also be "Dual Link." Few cable adapters are "Dual Link" and have a higher cost than "Single Link" cables. E-Port docks have "Dual Link" DVI connectors to allow all DVI cable types but are wired for "Single link" DVI resolution. They cannot be used for DVI connections requiring "Dual Link" DVI resolutions above 1920x1200.

• Question: Why cannot I get 2 different displays on a single DVI port using a splitter cable?
  Answer: A DVI port only transmits a single channel video signal. A splitter for a DVI connection merely splits the same signal and sends the copied (Cloned) signal to one or the other port on the splitter. You cannot use DVI splitters to extend the screen across 2 displays. Not all DVI splitters that are sold will work to clone and should be avoided unless all other options have been exhausted.
  
  Older video cards may contain a similar looking connection that is called DMS-59. A DMS-59 connection is designed to operate 2 displays in an extended configuration. DMS-59 is a legacy type connection and is not used in modern video adapters. This product is still available in limited product lines.

• Question: How many adapters can I use when connecting a display that has different ports than my video card?
  Answer: At the most, you may be able to configure your display with a single cable adapter. Anytime an adapter is added to a cable connection there is a signal loss in the conversion process. In almost all cases, using more than one adapter between the video card port and the LCD display will cause a degraded or loss of signal.

• Question: Why am I not getting a signal using a cable adapter?
  Answer: Cable conversions can only be digital to digital or digital to analog. (See Video Connection Information below)

• Question: My video card has 3 ports, why can I only get 2 displays to show?
  Answer: Because a video Adapter has 3 ports, does not mean that all three can be used at once. Many cards can only support any 2 displays on the 3 ports. It all depends on the specifications of the video card. Usually, you can only configure 2 displays, most cards have a dual channel video controller or 2 of the ports share a channel. Both setups are limited to two displays.
  
  Other cards may support 3 or 4 display connections. These require advanced DisplayPort connections and have specific limitations on any adapter configurations that might be used to connect displays. In general, 3 or more displays are configured using HDMI or DisplayPort technology. Either direct HDMI to HDMI connections, DisplayPort to DisplayPort connections or by use of Active DisplayPort adapters.
  
  Always check the manufacture specifications before trying to configure multiple displays.

• Question: What are the steps to get onboard (integrated) video working with an expansion (add-in) video card?
  Answer:
  1. Connect video directly to the expansion video card.
  2. Go into the BIOS and enable the "Multiple displays" option under Video (if this option is available).
  3. Boot into Windows and connect to the onboard video.
  4. Wait for the display to be detected.
  5. Restart the system.
  6. Load the Intel video driver for the onboard video.
  7. Restart the system.

• Question: Why do I get a message to disconnect my on-board DisplayPort when I add an expansion display adapter to my system?
  Answer: Depending on the system, you may have to disable the on-board graphics of the system or select the expansion adapter as primary display in the BIOS. You may also need to update to the latest BIOS version when you install an expansion display adapter in your system.

Video Connection Information

The best method for video performance and compatibility is to use a direct connection video cable. Examples are: DisplayPort to DisplayPort, HDMI to HDMI, or VGA to VGA

Most video cable adapters are not bi-directional cables, meaning video is converted in one direction. A DisplayPort to VGA signal is an example of a digital signal that is converted to analog. Sometimes analog video can be converted to a digital signal with an "Active" adapter, but is not guaranteed to work all the time.

There are two kinds of video adapter, "Active," and "Passive." The difference between an "Active" and a "Passive" adapter is a circuit that makes the conversion happen. "Active" adapters have a chip that makes the conversion happen while "Passive" adapters do not.

	Video "Input" on Monitor
Video "Output" on System		USB-C (Digital)	Display Port (Digital)	HDMI (Digital)	DVI-I (Digital and Analog)	DVI-D (Digital)	VGA (Analog)
	USB-C (Digital)	Straight Cable	Straight Cable	Straight Cable	Active Adapter Only	Active Adapter Only	Active Adapter Only
	Display Port (Digital)	Straight Cable	Straight Cable	Straight Cable or Passive Adapter	Straight Cable or Passive Adapter	Straight Cable or Passive Adapter	Straight Cable or Passive Adapter Only
	Mini Display Port (Digital)	Straight Cable	Straight Cable	Straight Cable or Passive Adapter	Passive Adapter Only   (no cable available)	Passive Adapter Only   (no cable available)	Passive Adapter Only   (no cable available) Only
	HDMI (Digital)	Straight Cable	Active Adapter	Straight Cable	Straight Cable or Passive Adapter (HDCP)	Straight Cable or Passive Adapter (HDCP)	Straight Cable or Passive Adapter
	DVI-I (Digital and Analog)	Active Adapter   Only	Straight Cable or   Passive Adapter	Straight Cable or   Passive Adapter	Straight Cable	Straight Cable or Passive Adapter	Straight Cable or Passive Adapter Only
	DVI-D (Digital)	Active Adapter Only	Straight Cable or Passive Adapter	Straight Cable or Passive Adapter (HDCP)	Straight Cable or Passive Adapter	Straight Cable	Active Adapter Only
	VGA (Analog)	Active Adapter Only	Active Adapter Only	Active Adapter Only	Active Adapter Only	Active Adapter Only	Straight Cable

*Most video cable adapters are not bi-directional cables, meaning video is converted in one direction.

More Information

The following links can be used to gather more details about general video information.

• A Guide to the External Ports and Connectors on a Dell Computer
• How to Troubleshoot Display or Video Issues on a Dell Monitor
• Troubleshooting video issues with a Graphics card fitted in a Dell Desktop PC
• Identifying the correct video connectors to use on your PC to prevent a No Video issue
• Computer Display Standard (Wiki)
• List of Video Connectors (Wiki)

If you have further questions about this article, contact Dell Technical Support.

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