Perhaps...
Anyway, that 3.5DISK line and the head select line are not controlled by the IWM, but by the VGC (graphics chip). (See page 3 and 4)
www.classiccmp.org/cini/pdf/Apple/Apple ... ematic.pdf
Gotta love it when unrelated functions migrate into a chip. Anyway, looking at the hardware reference, the disk interface register (page 153) sets the status of those two pins on the connectors. 3.5DISK pin 4 is "1" (pulled high?) when using 3.5" disks, and Head Select pin 16 selects which head of the drive to use.
https://archive.org/stream/Apple_IIgs_Hardware_Reference_HiRes#page/n175/mode/2up
Anyway, that 3.5DISK line and the head select line are not controlled by the IWM, but by the VGC (graphics chip). (See page 3 and 4)
www.classiccmp.org/cini/pdf/Apple/Apple ... ematic.pdf
Gotta love it when unrelated functions migrate into a chip. Anyway, looking at the hardware reference, the disk interface register (page 153) sets the status of those two pins on the connectors. 3.5DISK pin 4 is "1" (pulled high?) when using 3.5" disks, and Head Select pin 16 selects which head of the drive to use.
https://archive.org/stream/Apple_IIgs_Hardware_Reference_HiRes#page/n175/mode/2up