My reply in post #4 indicates the 4-primaries is effectively a PC standard. There are other software trying to get 255 primaries using different naming convention but they are not supported by Windows, Linux and Unix systems.
One can arrange a hard disk any way one sees fit but in loading any of the above systems the OS will automatically use the Bios information and go to 447th bytes to read the next 64 bytes assuming they are the partition table of the 4 primaries.
Both Grub and Lilo have no problem to read and boot the partitions in accordance with the PC standard.
From my own experience there is no operational advantage or benefit to use primary partitions in Linux and we can move a Linux in hda1 to hda63 and it will boot and operate just the same.
As the PC standard exists today with 4 primaries we could get a maximum of 240 partitions in a Pata disk. 236 Out of the 240 partitions will be bootable the remaining 4 as a combination of temporary primary and extended partitions.
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This is how one can get 240 partitions out of a Pata. I haven't exhausted the 240 limit myself but have tried 200+ partition before in
this thread.
The tools needed are fdisk, cfdisk and gparted. Gparted for the last few logical partition as cfidsk and fdsik stop reporting partition beyond the 60th partition.
(1) Use cfdisk to partition first logical partition. It will be called hda5 immediately and the first primary partition hda1 is used up the extended partition to house it. Proceed to make logical partition all the way to hda59. Write the partition table and reboot. After a reboot continue with gparted to make hda60 to hda63 logical partitions. Reboot again to make the first set of logical partition permanent.
(2) Hide the hda1, say using Grub or cfdisk, hda1 will immediately treated as an "unknown primary partition" and the logical partitions become invisible.
(3) Proceed with cfdisk and gparted on creating a new set of logical partitions which will be called hda5 to hda63 again. The second lot is inside the extended partition hda2. Reboot again.
(4) Hide hda2 thereby making it another "unknown primary partition" to Linux. The hda3 is again used to generate the 3rd set of 59 logical partitions. hda1 and hda2 remain unknown primaries and their logical partitions inside are automatically not displayed.
(5) Repeat steps (2) and (3) to get the last set of 59 logical partitions from hda5 to hda59.
In using any of them one just unhide the unknown primary and hide other 3 unknown primaries. The unhiden unknown primary turn back to an normal extended partition with the internal 59 logical partitions available for use and booting.
The above scheme works. One can write a set of Grub menus to boot all the 236 partitions inside. I am doing something similar but for a different reason.
I recommend the maximum logical partition number to be restricted to 63 to ensure at any one time there cannot be more than 64 devices from the Pata disk. The 64 should comprise of hda, 4 primaries hda1 to hda4 and 59 logicals from hda5 to hda63.
Personally I don't think many users are stretching the limits of the 4 primaries in a hard disk.