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How many displays can be used with Elgato Thunderbolt™ Dock? Last Updated: Nov 26, 2014 10:37AM PST

The number of displays you can use with Elgato Thunderbolt™ Dock depends on the power of your computer’s graphics system, the type of displays you’re trying to use, and whether you're using a Mac or PC.

The following is an exhaustive listing of how you can use up to two monitors with Elgato Thunderbolt™ Dock in various configurations.

To check to see if your Mac can support two monitors via Thunderbolt™, see Apple Technote http://support.apple.com/kb/ht5219#18

See the end of this article for a more technical explanation of why such limitations exist.

 
The Only Monitor is a DisplayPort Monitor


Mac:

You can use one DisplayPort monitor with the Elgato Thunderbolt™ Dock, by connecting it to the Thunderbolt™ port. 

This will work as long as no other monitor is connected to the HDMI port - if an HDMI monitor is connected, it will take precedence over the DisplayPort monitor, and the DisplayPort monitor will not work.


PC:

You can use one DisplayPort monitor with Elgato Thunderbolt™ Dock, by connecting it to the Thunderbolt™ port. 

This will work as long as no other monitor is connected to the HDMI port - if an HDMI monitor is connected, it will take precedence over the DisplayPort monitor, and the DisplayPort monitor will not work.

 
The Only Monitor is a HDMI Monitor


Mac:

You can use one HDMI monitor with Elgato Thunderbolt™ Dock.


PC:

You can use one HDMI monitor with Elgato Thunderbolt™ Dock.

 
The Only Monitor is a Apple Thunderbolt Display


Mac:

You can use one Apple Thunderbolt Display with Elgato Thunderbolt™ Dock. 


PC:

You can use one Apple Thunderbolt Display with Elgato Thunderbolt™ Dock.

 
One HDMI Monitor and One Apple Thunderbolt Display


Mac:

When using a powerful enough Mac, you can connect an HDMI display and an Apple Thunderbolt Display to Elgato Thunderbolt™ Dock at the same time.


PC:

When using a powerful enough PC that has two Thunderbolt™ ports, you can connect an HDMI display and an Apple Thunderbolt Display to Elgato Thunderbolt™ Dock at the same time.

Please Note:

On PC motherboards, only the boards with two Thunderbolt™ ports provide each port with two display signals.  In that setup, you would run one Thunderbolt™ cable from your PC to Elgato Thunderbolt™ Dock, but it would be carrying two display signals.

 
One HDMI Monitor and One DisplayPort Monitor


Mac:

When using a Mac, you can’t connect an HDMI monitor and DisplayPort monitor to Elgato Thunderbolt™ Dock at the same time.  The HDMI monitor will take precedence, and the DisplayPort monitor won't work.


PC:

When using a PC, you can’t connect an HDMI display and DisplayPort display to Elgato Thunderbolt™ Dock at the same time.  The HDMI display will take precedence, and the DisplayPort monitor won't work.


Please Note:

Any adapter that uses DisplayPort counts as a DisplayPort monitor for the sake of this article. That means you can't use a HDMI monitor and a DisplayPort adapter at the same time.  The HDMI monitor will take precedence, and the DisplayPort adapter won't work. 

For example:

• A DisplayPort to DVI adapter can't be used at the same time as a HDMI monitor.
• A DisplayPort to VGA adapter can't be used at the same time as a HDMI monitor.
• A DisplayPort to HDMI adapter (which may be called a Thunderbolt™ to HDMI adapter) can't be used at the same time as a HDMI monitor.

Other combinations using various standards also won't work.

 
Two Displays Via Two Thunderbolt™ Docks


Mac:

You can connect an HDMI display, and then connect the Elgato Thunderbolt™ Dock to another Elgato Thunderbolt™ Dock via a Thunderbolt™ cable.

Then, the second Elgato Thunderbolt™ Dock can connect to a display via Thunderbolt™, HDMI or DisplayPort.


PC:

When using a powerful enough PC that has two Thunderbolt™ ports, you can connect an HDMI display, and then connect Elgato Thunderbolt™ Dock to another Elgato Thunderbolt™ Dock via a Thunderbolt™ cable.

Then, the second Elgato Thunderbolt™ Dock can connect to a display via Thunderbolt™, HDMI or DisplayPort.

Please Note:

On PC motherboards, only the boards with two Thunderbolt™ ports provide each port with two display signals.  In that setup, you would run one Thunderbolt™ cable from your PC to Elgato Thunderbolt™ Dock, but it would be carrying two display signals.

This setup won't work on Macs in Bootcamp.

 
One Thunderbolt™ Dock Can Only Run Two Displays At A Time


Mac:

The Thunderbolt™ signal from a Mac has up to two display signals in it.  Therefore, no more than two monitors can be connected to Elgato Thunderbolt™ Dock at the same time.


PC:

The Thunderbolt™ signal from a PC usually only has one display signal in it. 

The exception is a PC that has two Thunderbolt™ ports. Only PC motherboards with two Thunderbolt™ ports provide each port with two display signals.  In that setup, you would run one Thunderbolt™ cable from your PC to Elgato Thunderbolt™ Dock, but it would be carrying two display signals.

No more than two monitors can be connected to Elgato Thunderbolt™ Dock at the same time.

 
Exceptional Cases


1) DisplayPort monitors will not function if connected to the Thunderbolt™ port of an Apple Thunderbolt Display.

See Apple Technote http://support.apple.com/kb/ht5219#20

2) Any monitors cascaded after an Apple Thunderbolt Display won't work.
 
 
Why Are There Restrictions On How Many Displays Can Be Used?


Thunderbolt™ has PCIe and DisplayPort signals multiplexed together. 

There can be up to two DisplayPort signals available on the Thunderbolt™ bus, depending on the Mac or PC.

When the DisplayPort signals come from the computer over Thunderbolt™, and travel into the Elgato Thunderbolt™ Dock, one of them is demultiplexed.  That DisplayPort signal is ready to be used.

The demultiplexed DisplayPort signal is translated by the Elgato Thunderbolt™ Dock into HDMI.  That leaves one DisplayPort signal still multiplexed in the Thunderbolt™ signal, for later use in the Thunderbolt™ chain.

That second DisplayPort signal can only be demultiplexed by another Thunderbolt™ device, like the Apple Thunderbolt Display, or by another Elgato Thunderbolt™ Dock.

If you connect a DisplayPort monitor to the Thunderbolt™ connection when the HDMI port is in use, the DisplayPort monitor will not light up. In this case, only Thunderbolt™ signaling is available at the Thunderbolt™ connection, which the DisplayPort monitor does not understand.

When you try to connect two non-Thunderbolt™ monitors to the Elgato Thunderbolt™ Dock, you can either get a signal over the HDMI port, or via DisplayPort, but not both at the same time.

If you choose to use a HDMI device, then one multiplexed signal remains, associated with the Thunderbolt™ port, available for Thunderbolt™ devices only.

If you choose DisplayPort (via the Thunderbolt™ port), then the Thunderbolt™ bus is terminated, when it comes to display signals.  The DisplayPort monitor will work, but the HDMI port will not. 
 

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