Page "X Window System" Paragraph 67

Like all thin clients, when using X across a network, bandwidth limitations can impede the use of bitmap-intensive applications that require rapidly updating large portions of the screen with low latency, such as 3D animation or photo editing.

Even a relatively small uncompressed 640x480x24bit 30fps video stream can easily outstrip the bandwidth of a 100Mbit network for a single client.

Early versions of X would suffer even when not using the local network, such as when using a linux workstation with the X server and client on the same system, due to the network-centric protocol which would still utilize an internal network model within the computer, via localhost or unix sockets.

In contrast, modern versions of X generally have extensions such as MESA allowing local display of a local program's graphics to be optimized to bypass the network model and directly control the video card, for use of full-screen video, rendered 3D applications, and other such applications.