[Qemu-devel] Problem with `change' monitor command

[Robert Riebisch]

Hi!

I'm using QEMU 0.9.1 and SVN on Win32 to emulate an x86 PC environment.

With `change floppy0 foo.img' I'm able to use another floppy image on
the fly, but this will only work, if the new floppy image is of the same
size as the old one. Switching from, e.g., 1.44M to 2.88M is not
recognized by the guest OS. Even rebooting the VM doesn't help, because
CMOS value 0x10 ("Floppy Drive Type") won't be adjusted.
(http://www.brl.ntt.co.jp/people/takehiko/interrupt/CMOS.LST.txt)

This is also a big problem when you omit "-fda bar.img" from the command
line. You can still change the image file in QEMU monitor, but guest OS
(here: DOS) will never recognize it, because CMOS value 0x10 still holds
"0" (= "none" for floppy0 and floppy1). Btw: It would be more
consistently to also change command-line option "-fda" to "-floppy0".

For demonstration I quickly wrote a minimal DOS tool using free Turbo
Pascal 5.5 to decode this value. Just tell me, if anyone is interested
in the binary and source code (very simple). I could also provide a
bootable disk image (FreeDOS + my tool).

Robert Riebisch
-- 
BTTR Software
http://www.bttr-software.de/