Double sided 8" floppy in SA800 drive

Not directly. The single-sided and double-sided disks have the index hole (in the jacket) in a different place. The single-sideed (single head) drive had one indexc sensor, to line up with the hole in the single-sided disk. The double-head drive (SA850, etc) has 2 index sensors, one to line up with each hole. Of course when a particualr disk is inserted in a double-head drive, only one index sensor will be active (the other will be blocked by the opaque disk jacket), and by detecting which sensor is active, the drive can signal to the conttoller whether it's a single or double sided disk. If you want to use some blank double-sided disks in a signle-sided drive you need to punch and extra hole in the jacket (and really, block up the exisitng hole in case they are aver put in a double-head drive). Yes, but in that case you need to punch another index hole so that the index sensor can work when the disk is flipped over. 8" disks have the write-protect notch covered to enable writing (the oposite of the 5.25" convention, and IMHO a lot more sensible) so you don't need to cut another write-protect notch unless you want to be able to inhibit writing to the other side of the disk). Of course this will not allow you to read or write a disk that is to be used ina double-head drive. The second side will be recorded backwards -tony