copy to a phantom B: drive soft-fails sometimes (int 24h)

[mateuszviste]

boot the attached floppy image with:

qemu-system-i386 -fda floppy.img -vga cirrus -m 4M -cpu 486 -machine isapc -no-hpet

Then, in the DOS prompt:

COPY BIG.A B:\BIG.B

Then press any key 8 times (no need to actually swap any diskette). Result:

Interestingly, if one chooses to (R)etry, then the operation eventually finishes and the copy is successful (confirmed by pkg crc32 big.a).

Now do a COPY KERNEL.FD KERNEL.SYS and restart the VM. Redo the test: it works fine and a proper copy is performed.

Secondary issue

If you look at the int 24h message, it says a write error occurred on drive A:. This is confusing because the destination was B:, not A:. I suspect that when the kernel issues the int 24h call, it forgets to translate the drive letter and keeps the BIOS id.

PS. also tested with VBox, same results