The DR-DOS/OpenDOS Enhancement Project

Yes, you are right. EDR-DOS does not mount the last partition.
I did not pay attention to the CHS values returned by Partinfo until
I read your message. I do not know for sure where they came from, but
probably it was from the wrong results returned by int 13 fn 08. The
correct CHS values, from the disk datasheet and from the table pointed
to by int 41 are 1651/10/63 or, last cylinder=1650, last head=0F,
last sector in track=63. Moreover, since this BIOS int 13 accepts 4096
cylinders I have read/write/format access to all the disk using int13.
I think the best option is to change the way EDR-DOS checks the
disk geometry, or do not check at all. No DOS other than EDR-DOS seems
to use function 08 and never had any problem resulting from this.
Even if you prefer to keep EDR-DOS as it is, thank you very much for
your help.