If a Quantum PRO drive was originally initialized with Apple HD SC Setup 2.0,
the HFS partition would be larger than if it was initialized with Apple HD SC
Setup 2.0.1. The reason is that the PRO drives were not directly supported by
Apple HD SC Setup 2.0 (the drive did not exist yet!). However, because it was
an Apple drive, the Apple HD SC Setup 2.0 software supported the drive with
generic, Apple-drive settings. The size of the HFS partition was rounded down
to the closest 20MB. Therefore, under Apple HD SC Setup 2.0, the HFS partition
was 160,000 blocks (even).
Apple HD SC Setup 2.0.1 included changes that added direct support for PRO
drives and the Macintosh IIci. (See the "System 6.0.5 Final Change History"
for details.) The default HFS partition size for each drive is in an internal
lookup table. The number of blocks allocated on a standard, known 80MB drive
is 156,270 blocks. This size has been dictated by the original Quantum Q280
5.25-inch drive that had only 156370 blocks. To make ALL 80MB drives look
alike (at least on the surface), we standardize on one 80MB partition size.
Therefore, if you had a PRO 80s drive, and you initialized it with Apple HD SC
Setup 2.0 software and then went to Apple HD SC Setup 2.0.1 software, you would
have lost 3730 blocks of storage or about 1.5MB. A workaround would be to use
the CUSTOM partition screen, remove the original HFS partition, and create a
new one manually, which is 80,000K.