The 1541 disk drive was infamously slow, probably the slowest of the 8-bit floppy disk drives, the result of a VIC-20 Kernal bug that was inexplicably kept in the C64 for the sake of backwards compatibility. The problem could be fixed by writing your own disk routines, which is why so many games used fastloaders.
But the bug isn’t always at fault. The 1541 disk drive takes over a minute and a half to format a disk, but as it turns out it had good reason to, and the time consumed had nothing to do with the C64’s code because the drive does all the work itself; the Commodore 64 just waits throughout the process.
Commodore History goes into considerable detail on the process here (16½ minutes). During formatting the drive wipes out all the data that had been on the disk, lays down syncing structures, writes the disk ID to every sector, puts down the directory track and sets up the Block Allocation Map (BAM), and more. It’s an interesting, if not too useful these days, exploration of what disk drives at the time had to do to make the disk’s magnetic surface usable for data storage.
