You can increase the speed of a serial connection over a pipe to a virtual machine.

In principle, the output speed, which is the speed at which the virtual machine sends data through the virtual serial port, is unlimited. In practice, the output speed depends on how fast the application at the other end of the pipe reads inbound data.


  • Use the guest operating system to configure the serial port for the highest setting supported by the application that you are running in the virtual machine.
  • Power off the virtual machine and exit Workstation Pro.


  1. In a text editor, add the following line to the virtual machine configuration (.vmx) file.

    serialport_number.pipe.charTimePercent = "time"

    port_number is the number of the serial port, starting from 0. The first serial port is serial0. time is a positive integer that specifies the time taken to transmit a character, expressed as a percentage of the default speed set for the serial port in the guest operating system. For example, a setting of 200 forces the port to take twice as long for each character, or send data at half the default speed. A setting of 50 forces the port to take only half as long for each character, or send data at twice the default speed.

  2. Assuming that the serial port speed is set appropriately in the guest operating system, experiment with this setting by starting with a value of 100 and gradually decreasing it until you find the highest speed at which the connection works reliably.