and also a wire that runs to a jumper on top of each floppy drive. Not sure what it does.
By the way, these (white wires in my photo of the NEC dual floppy box) run to the RD header on each of the floppy drives, this enables VFO/VCO. Indeed inside the floppies there are 19.2 MHz and 16 MHz oscillators right near these pins just like kitahei88's circuit.
You can find the VCO schematic there : http://24.dtiblog.com/k/kitahei88/file/ ... ematic.pdf
There are 2 signals coming from the computer : one to select the VCO mode : FM or MFM, and the other to select the bitrate.
Should it be better to use the HxC through the interface inside the dual-drive enclosure or going directly to the computer?
mhh in fact this is as you want.
I don't quite understand if these wires are enabling this in response to detected SYNC/WINDOW commands and superflous for HxC+VCO circuit purposes (but maybe helpful for me to find out if the computer is sending these commands) or what.
These signals are needed since the computer need to be able to change the VFO mode.