Specifications

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VMware GSX Server Virtual Machine Guide
Special Configuration Options for Advanced Users
Two special configuration options are available for serial connections between a
virtual machine and the host or between two virtual machines. These options are of
interest primarily to developers who are using debugging tools that communicate
over a serial connection.
Improving Processor Performance When Debugging
The first option must be set in the virtual machine settings editor (VM > Settings >
Serial Port) or the VMware Management Interface (Configure Hardware > Edit next
to the serial port). This option is useful when the serial port is being used by the guest
operating system in polled mode as opposed to interrupt mode. Polled mode causes
the virtual machine to consume a disproportionate share of processor time. This
makes the host and other guests run sluggishly.
To restore performance for applications on the host, check the Yield CPU on poll
check box. This configuration option forces the affected virtual machine to yield
processor time if the only task it is trying to do is poll the virtual serial port.
Changing the Input Speed of the Serial Connection
To use the second option, power off the virtual machine and close the console
window, then use a text editor to add the following line to your virtual machine’s
configuration file (.vmx):
serial<n>.pipe.charTimePercent = <x>
This option is useful if you want to squeeze every possible bit of speed from your serial
connection over a pipe to the virtual machine. In principle, there is no limit on the
output speed — the speed at which the virtual machine sends data through the
virtual serial port. In practice, the output speed depends on how fast the application
at the other end of the pipe reads data inbound to it.