China DOS Union

Use a USB flash drive to create a bootable disk. Initially, using USBoot for booting was okay. Then using the latest DiskGen 3.8 was also okay. Then using the USB boot maintenance disk making tool produced by Shenzhen Deepin didn't work. The DOS couldn't boot. Although the PE was okay, as a system maintenance disk, it was too unreliable. So, going back to use USBoot to make a DOS boot again, it wasn't recognized. After carefully examining the reason, it was found that there was a dispute between two types of DOS, one was Microsoft's MSDOS, and the other was the newly emerging open-source FreeDOS. Looking at the prompt where the boot failed to stay:
Old: int13=e73488c5 int15=f000f859
New: int13=9ec00008 int15=9ec00376
Loading boot sector … booting…
The problem is how to delete the FreeDOS boot information so that the MSDOS 7.1 boot installation can be carried out?
Do we need to use DEBUG, and how to use it. Using SRCTools, we can't find it and don't know how to modify its boot sector data.

After using FREE DOS to make a boot, when using MSDOS to make a boot, it becomes invalid. Then, how can we remove the MBR data retained by FREE DOS?

I think rewriting the MBR is enough. The DOS used by DiskGen is freedos. Then it seems that USBoot uses ms-dos.

However, on some buggy (with many bugs) motherboards, when booting with msdos, the USB flash drive may not be accessed normally, but it works normally with freedos, because MSDOS does not support LBA mode to access the USB flash drive, while freedos does.

See the discussion in this post:
http://bbs.znpc.net/viewthread.php?tid=5335&page=3&fromuid=16#pid32951

Methods to rewrite the MBR: You can manually edit with tools like WinHex, or use Diskgen for Windows to rewrite the master boot record (this operation should always be safe). You can also treat the entire USB flash drive as the hard disk of a VMware virtual machine (treating the real physical disk as the hard disk of the VM), and then boot into DOS in the virtual machine, and use fdisk /mbr to rewrite. In short, there are many methods, depending on which is convenient for you to play.

[ Last edited by Climbing on 2008-11-17 at 16:57 ]

Thanks! The train of thought is correct.
However, the master boot record rewritten by Diskgen for Windows is still of FREEDOS. Using fdisk /mbr cannot enter the DOS system. I haven't tried it in the virtual machine, but it should be possible to manually edit it with tools like WinHex.
Also, the discussion in the post is quite worthy.
Thanks again!

Decided to give up using MSDOS 7.1 for USB drive boot system and switch to FREEDOS system. Of course, floppy disk is still better with MSDOS 7.1, after all, some software cannot be operated under FREEDOS system.

The latest DISKGEN 3.0.830 can directly make FREEDOS boot USB drive, and various DOS software can be added, but it needs to be tested to prove whether it is applicable. TW Chinese can be used on it, some DOS commands can directly use FREEDOS, and the startup files FDCONFIG.SYS and FDAUTO.BAT should be rewritten according to their own needs.

Then, use Lao Mao Tao's PE making program "WinPE (Lao Mao Tao final modified version) V09.11 Simplified Chinese" to add GRUB boot. The specific method is, do not format, and check the boot making "prioritize booting original MBR" is okay.

The final result is that it is very convenient to make DOS + PE boot system on USB drive.

Only how to customize PE system is a problem. Directly modifying WINPE.INI can uninstall some programs, but cannot delete, and cannot add. Downloaded AIK, very tedious.

Also, originally planned to boot GRUBD from FREEDOS, can also be successful, but subsequent Menu.lst processing is not okay, cannot use. I wonder if GRUBD should be in the root area.