Which systems use the index hole in 5.25" disks?

[matsondawson]

??

[tezza]

Hmm..not sure. I know standard Apple II drives didn't.

[TRS80]

I believe most machines that use a Western Digital Floppy Disk Controller (1771 or 1793) rely on this. Some PC controllers also rely on it and have trouble reading TRS-80 disks generated by some operating systems because there is insufficient gap after the index hole before the sector starts.