Haven't investigated thoroughly, then, is it just me, or... ? It appears though Grub4DOS won't recognize/mount
a FAT16 partition as soon as the third byte of the jump instruction at partition boot-record (PBR) offset zero, usually :
Jmp short Start NOP
... was changed from 0x90 to anything else, including 0x0E (which, as one knows, some boot code variants
use as a hint to make only extended int 13 calls).
Restoring the byte sufficed to restore Grub4DOS's ability to mount, access, and boot from, the partition !
Issue noticed while using G4Dos 0.4.6a-2019-10-28 (Chenall's). As said, I've not investigated further yet
w/ other FAT types, G4DOS versions, or other variations off the regular boot record.
Waiting to hear from you all if this is a confirmed, even expected (?) quirk, is it version specific and of course
hoping for a fix if this is confirmed as a bug.
Edited by Ninho, A week ago.