Mouse Races and Jumps Across Screen

Your mouse pointer races across the screen in sudden bursts. It is difficult to control and often goes beyond what you aim for.

You have a serial mouse connected to a port based on the 16550 UART chip. The port adapter or motherboard uses hardware buffering rather than software buffering; and, the buffer is turned on. The mouse races because the hardware buffer is caching mouse movements and releasing them to the mouse driver in blocks. The mouse driver interprets these streams of movements as accelerated input and drives the mouse pointer accordingly.

Disable the hardware buffering for the serial port the mouse is connected to, or choose a different port.