and I don't know the math exactly
Well, it's quite simple:
Each HDD consists of several disks with two surfaces each. This is just like several floppy disks lying on a stack.
So a HDD with 8 disks has 16 surfaces. Each surface is accessed by one read/write head. So the number of surfaces equals the number of heads.
Now each surface is divided into tracks. Tracks are concentric circles on the disk. Each track in turn is divided into an equal number of sectors.
The collection of the same track on each surface forms a cylinder, so the number of heads is the number of tracks per cylinder.
Now the mathematics:
sectors per track * tracks per cylinder = sectors per cylinder (easy, isn't it ?)
sectors per track * tracks per cylinder * cylinders per drive = sectors per drive.
bytes per sector * sectors per track * tracks per cylinder * cylinders per drive = bytes per drive.
The same with other words:
bytes per block * sectors * heads * cylinders = capacity.
Well, actually a
sector should refer to the physical unit as used above, while a
block should refer to the logical unit used by the file system to allocate space. A block consists of one or several sectors.
But even in the official AmigaDOS documentation the terms sector and block are totally mixed up, so you have to understand the context in order to know which one is meant.
Bye,
Thomas