I don't know of any reason why any Mac with an IDE connector can't support LBA-48 except for the drivers. Drivers can be replaced.
The Open Firmware driver needs to be updated for Mac OS X to load "BootX" unless it's on a helper partition (setup by XPostFacto for example).
The Open Firmware driver needs to be updated for Mac OS 9 only for New World Macs to load the "Mac OS ROM" file. I don't think OS 9 has a helper partition concept which would allow "Mac OS ROM" to be loaded from a reachable partition but have the rest of the system on a different partition. But "Mac OS ROM" has Open Firmware code that can be modified, so maybe it's possible?
One can load a newer Open Firmware driver from a reachable partition. I've done this for Beige G3 with Open Firmware 2.4.
BootX loads a Mac OS X driver. For OHare and Heathrow and Paddington IDE (also CMD646 IDE), the Mac OS X driver needs to be replaced. I've created the replacement kext but haven't tested it yet.
For partitioning large disks, I would use Mac OS X Leopard which still has the "Install Mac OS 9 Drivers" option.
https://github.com/dingusdev/dingusppc/issues/177#issuecomment-4417830475
https://forums.macrumors.com/threads/cant-boot-from-firewire-drive.2478368/post-34454141
https://tinkerdifferent.com/threads/bondi-blue-imac-restoration.5481/post-48786
For testing, the drive should be partitioned on a computer that supports LBA-48. Then you have to see if the older computer can access all the partitions in Open Firmware, Mac OS 9, and Mac OS X.
Macs with OHare (can boot Mac OS X with XPostFacto?)
- Alchemy: 5400, 6400
- Gazelle: 5500, 6500, TAM
Macs with Heathrow:
- Gossamer: Beige G3
- Lombard G3
Macs with Padington:
- iMac Bondi Blue
- Yosemite B&W G3, G4 Yikes
Macs with CMD646:
- Yosemite B&W G3, G4 Yikes
How to verify that LBA 48 is supported? I'm not sure. You could try writing the block number to every block of a disk, then read them back. That is the surest way.
Third party IDE controllers may have LBA-28 limit. Some may have a LBA-48 patch (some Sonnet cards). If they don't have source code, then it would difficult to update them yourself.
elephantandchicken.co.uk