@buzz
Yes I did check the syntax using "1581 ?". It was the device argument I wasn't sure about - I didn't know whether to put C0, DF0, or just 0. Have just tried it using:
1581 0 supremacy.d64 write
and I got some message about an error reading the image file, then it started writing tracks and seemed to complete ok, but then the disk was not readable on the C64 :-?
--
moto