The new drive I put in was blank and thus I used the 'use entire disk' option, and the sum of the partitions is about right. It definitely does not do a full spec format.
For example, (from my days at the IBM Disk manufacturing plant Havant England) The format routine does nothing other than issue a block command for the drive to fill it's buffer with sequential chunks of data, read the checksum bytes (taken from the disk) and then compute the data checksum for the data in the buffer (it computes the checksum 'on the fly'. If the two checksums agree then the data is considered good, if not then there may be upto 500 yes, 500 retries (1 retry per rev) at 7200RPM a full set of retries takes only 3-4 seconds. Any single retry that is successful is good enough for MS to consider the drive as good. At the end of all this no data has been written to the disk until a map is drawn up detailing any bad clusters (groups of sectors), then finally the boot record is re-written. Incidentally floppy disks are formatted cortrectly, ie a data pattern is written to then read back from, the disk.
for a 320Gbyte drive to format in three minutes would require a diskwrite speed of the order of 20 billion bits per second which would mean a write frequency around 3 times that.