Extra axes can be added up to a total of 8. With your own computer, this would be all you need to cut parts. You can also select from ready-made enclosures. Using the motion card hardware method has been the industry standard for many years and known to be proven with over 200,000 motion cards shipped to date. Off loading the closing of the servo loop to a dual processor provides reliable servo update times up to within 62.5 microseconds resulting in cutting feedrate velocities of up to 122,000 IPM which is far greater than today's servo motor technology.
Dual processors allow multiple events and multiple positioning motions to happen simultaneously.
Closing the servo loop has to be a very tight algorithm and consumes a great deal of CPU time cycles. One could imagine how the main computer's CPU could keep up with all the other tasks it is asked to perform. For example, when using a dual processor, 3D profiles can be cutting at the same time a tool change is taking place or a servo motor positions a rotary table. We all have to admit to the extra safety a dual processor offers if the computer pauses, fails or locks up. The computer's CPU was never designed to close such an intensive task as a servo loop and still process other events.