Gordon,
GB> My question is not an HFSx one per se, however, it's it in the GB> ballpark: Since OS X.3 came along, the partition map is now being GB> populated by default with a number of Apple_Free partition entries GB> interspersing the user's specified partitions. I'm curious whether GB> anyone knows the rationale behind this. I have my theories but I'm GB> probing for a more definitive response, if one exists.
Not quite sure being on the spot, but since the Apple specs say that the whole space on a disk must be allocated in the partition map, it can happen that the division between the main partitions (driver partitions, payload partition, etc.) doesn't make the total of the sectors on disk. The rest should be represented in the partition map by a Apple_Free partition.
My 2 cents...