Overview

Modern computers are limited in regard to the number of external displays that can be directly connected or “natively supported.” These limitations are determined by the capabilities of the host computer’s internal graphics processing unit (GPU) and the number of physical video connection ports available.

Products available from Plugable that use technology from DisplayLink or Silicon Motion provide the ability to connect multiple external displays to a computer via USB once the required software driver is installed, which allows one to workaround the host computer’s internal limitations.

Such technologies are typically referred to as ‘indirect display’ technologies because the USB connection means that the displays are NOT connected directly to the host computer’s GPU.

The total number of external displays possible via an indirect display technology can vary due to a number of factors:

- The technical specifications of the host system

- Limitations of the host operating system in regard to how many displays can be addressed

- Limitations of the USB subsystem, in regard to how many devices can be physically connected and recognized by the host system

- The capabilities of the specific indirect display technology in use

Speaking in general, with most modern computers at least four external displays can be added via USB graphics technologies and in some instances up to eight displays are possible. Note these are in addition to the number of native external displays your system supports, which ranges from 1-4 on most modern systems.

Number of indirect displays supported by Plugable

A. Total includes any displays added via Apple’s Sidecar feature → https://support.apple.com/en-us/102597

B. Performance is dependent upon the specifications of the host system. Chromebooks using lower-spec CPUs and GPUs may support fewer displays

*** Please see important information within the ‘Performance and Technical Limitations section below ***
 

Performance and Technical Limitations

When using products based an indirect technology, the number of external displays that can be added to a computer (and are supported by Plugable) will vary depending upon which operating system is in use and certain technical limitations:

Host resource use

An indirect display device is in essence a ‘virtual’ GPU that relies on the capabilities of the host computer’s CPU and physical internal GPU in order to generate the image shown on the attached displays.

With each indirectly connected display added to the host, more CPU and GPU resources are required. As more displays are added, the amount of resource use may impact both the performance and stability of the computer and displays. It should be noted that the resource load will vary depending on the type of content being shown within the indirectly connected displays. For example, static content (such as an office application) will require less resources as compared to dynamic content (such as a video).

USB device connection limit

Modern computers have practical limits in regard to the maximum number of devices that can be connected to the host’s USB subsystem.  

These limits will prevent USB devices from being recognized by the host when a certain number of devices are connected.

The total number of USB devices that can be connected can vary from system to system, as well as the specification of the USB protocol in use.

Speaking in general, host computers that supported only USB 2.0 could recognize and use a large number of external USB devices.

Host computers that support USB 3.0 or later versions of the specification have limitations in regard to the number of external devices that can be connected to ensure the level of performance does not drop below a certain threshold.