The beige G3 came out in 1997, a year before the Int 13h extensions became available on the PC, although this really didn't apply to Macs. Going by the presence of the IDENTIFY DRIVE command and PIO4 transfer rates on the circa 1994 Performa 630 series, one could assume the original code targeted the ATA-2 standard. This fully supported direct 28-bit LBA access to drives, but Apple clearly didn't use it in their ROM driver. The now legacy CHS addressing was limited to 24bits, thus the silly 8.4GB limit.