Steve has hopefully already reduced the kernel speed as I mentioned it early in this thread (#17). Perhaps not I was not forceful enough.

If it's 800step/rev then on 25kHz with 10mm pitch screw and direct drive the maximum feed is 25000/800*10*60=18750mm/min ... so plenty. Clearly half that with 1600, which it sounds like is still a lot more than your machine will currently do.

The only time I've used more than 25kHz is experimenting ... when I got 1m/s feed on Y-axis that was with a higher kernel speed. I've also monitored the port at 100kHz with oscilloscope and interestingly it seemed fine.