A CPU selectively programs one or more graphics devices by writing a
control command to the command buffer that designates a subset of
graphics devices to execute subsequent commands. Graphics devices not
designated by the control command will ignore the subsequent commands
until re-enabled by the CPU. The non-designated graphics devices will
continue to read from the command buffer to maintain synchronization.
Subsequent control commands can designate different subsets of graphics
devices to execute further subsequent commands. Graphics devices include
graphics processing units and graphics coprocessors. A unique identifier
is associated with each of the graphics devices. The control command
designates a subset of graphics devices according to their respective
unique identifiers. The control command includes a number of bits. Each
bit is associated with one of the unique identifiers and designates the
inclusion of one of the graphics devices in the first subset of graphics
devices.