I have a 12MB HDD image with FreeDOS installed on it (fdos.img). The image is on a bootable USB pendrive (/boot/fdos.img). It has valid MBR and one active partition. Grub4Dos is installed on this pendrive with this menu entry for dos:
title FreeDOS map --mem (hd0,0)/boot/fdos.img (hd0) map (hd0) (hd1) # map --a20-keep-on=0 # map --int13-scheme=0 map --hook rootnoverify (hd0) chainloader +1 map --floppies=0 map --harddrives=2 boot
If I boot this pendrive in qemu it works fine. Drive C: is FreeDOS (fat12) and D: is pendrive (fat32). Both disks are accessible from dos.
But in my real PC there is a problem. I boot it with option USB-HDD. FreeDOS loads fine but disk D: (USB pen) is empty! It looks like valid, it's size is valid but no files are shown with DIR command. If I use syslinux+memdisk instead of grub4dos the same problem occurs. What can it be? I need an access to other files on USB too.
Second issue is a crash of Jemm386 (freedos mem emulator) exception 06. Also no problem under qemu, only under real PC (and only with grub4dos, memdisk works fine here)