The slicer will generate a command that says go from point (x1, y1, z1) to point (x2, y2, z2) with speed f, but it doesn't say anything about acceleration, or how to transition into the next move. A very simplistic controller will use a trapezoidal ramp profile where it will ramp up to the programmed feed rate at a fixed acceleration, then stay at the programmed feed, then ramp down in time to reach the end point. However, if the move was a very short line or arc as part of a large surface, the machine doesn't need to reach 0 speed before starting the next move. A smarter controller will 'look ahead' to predict the next few move and plan the motion of the machine to eliminate jerkiness or stopping.

The slicer may tell the machine what acceleration to use, but that's really just setting a parameter in the machine controller, and isn't settable per-move.

This isn't as critical for 3D printers as it is for big, heavy milling machines. Nevertheless, you can do clever things like trying to compensate for vibration, or speeding up or slowing down the extruder motor based on the pressure of the plastic in the nozzle.

This isn't to say Prusa is switching just to do better motion planning, it sounds like that isn't a primary goal, but I'm trying to illustrate there is a lot more room for intelligence than 'just wiggling some IO'.

I mean sure, it's not going to be a perfectly smooth transition, but I think you're underestimating how bad it was on the Atmega. There is _no_ code space left on those chips, which makes adding features nearly impossible. They'll probably just maintain the old version for as long as they can, while switching new products over to the new one.

The codebase is also probably simpler than you realize. These microcontrollers don't have the code space for programs of any significant size. Porting the peripheral interfaces over to the new controller is not that hard.

> (As for the motion control aspect, at the feedrates of 3D printers, I don't think you get anything from a faster processor. Motion control is not what's limiting print speed or accuracy.)

This is actually a real problem. It's not the basic motion control, but doing things like intelligent look-ahead or vibration compensation.

I think the technology is further ahead than you realize. It's not an Atmega running your microwave we're talking about. Those chips _are_ seriously limited, in material ways, even if you haven't run into it yourself.

iirc they have well over 200 employees at this point.