Hardware quick-fire questions

Why do some old Macs use 800Kb floppy disks?

On the early classic Macs, Apple used a custom drive controller that varied the voltage to the drive motor. This made it spin slower when the drive head was near the outer edge of the disk than when it was near the middle. Because the circumference increases as you move outwards, there is more room for data and varying the speed means that none of the available space is wasted. Apple was able to squeeze 800Kb on a floppy, instead of 720Kb for a standard single-sided floppy. Unfortunately, they were incompatible with any other system and Apple abandoned the technology soon after. Which classic Macs can use 1.44Mb floppy disks? The SE FDHD, the SE/30, the Macintosh Classic, the Classic II and the Color Classic.