"Unlike other software such as KCam and Mach2, DeskCNC requires an interpreter board (DeskCNC controller). "
If you think of it as a breakout board, things may come into perspective when comparing to parallel port controllers. It is however an intelligent breakout board with direct e-stop, feed hold, cycle start, and probe/limit inputs, and output relay control signals for spindle speed and direction and flood and/or mist coolant. Because the hardware control is on the controller chip and not tied to the parallel port, it is also possible to use a USB to serial adaptor.
"The result is faster and smoother motion than is normally possibly under windows."
That is correct. About 45,000 smooth steps per second on a "dumpster grade", Windows 98 (or later) computer, which is also faster than many DOS controllers can meet. All 4 axes can be pulsed at this rate at the same time.
"what is meant by "Circular Interpolation". So, what does this mean and what are the implications should you not have identical pitches on X and Y?"
With DeskCNC, circular and linear interpolation are implemented within the controller in hardware. Circular interpolation requires that both axes have the same step ratios. If you want to cut an arc and you don't have the same ratios, you are attempting to do elliptical interpolation. Elliptical interpolation is not implemented in hardware, but it IS implemented in software. For most users this will be a distinction without a difference.
However at extremely high feedrates (and greater than 300 motion blocks per second), the software interpolation throughput may limit the top speed. An arc takes only one motion block whereas an ellipse can take many. Hence a significant speed increase if both axes have the same ratios and arcs are used in the G-code.
Fred Smith - IMService
http://www.cadcamcadcam.com