However, there already is a certain amount of free space allocated for this task. On the Intel drives, it's the difference between 80GiB and 80GB; the latter is

However, there already is a certain amount of free space allocated for this task. On the Intel drives, it's the difference between 80GiB and 80GB; the latter is the maximum addressable by the OS, the former is the actual capacity of the flash chips. Flash chips always have a power-of-2 capacity, and there are 5, 10 or 20 chips in the various intel drives.