To be more extensive on the solution i found (Using only Mac OSx and Parallels Desktop)
The boot loader, although the source (FpLoader.s) could be a bit more elegant (reserve a stack zone, set the sp, ...), is ok. The compilation can be done with:
nasm -f bin FpLoader.s -o FpLoader.bin
This should give you a binary file of 512 bytes.
When using (eventually with sudo)
dd if=FpLoader.bin of=FpLoader.iso bs=2k
an iso file of 512 bytes is created. This iso does not contain a second, nor following 'disk' sectors. I presume that the Parallels Desktop verification checks this and blocks the use of such an iso file.
So, we need an other solution: create an entire empty disk (floppy in this case) onto which we write the content of our binary file (in the first sector).
This can be done as follows:
dd if=/dev/zero of=FpLoader.img bs=1024 count=1440
diskutil eraseVolume MS-DOS FPLOADER `hdiutil attach -nomount FpLoader.img`
dd if=FpLoader.bin of=FpLoader.img bs=1 count=512 conv=notrunc"
The first command fills up an empty floppy image of 1.4 Mb, the second command overwrites the first sector with our boot loader.
Within Parallels Desktop One can create an Ms-Dos alike virtual machine with very little resources:
Memory: 4 Mb
Hard disk: 2 Gb
Devices: Hard disk and Floppy disk (even Cd drive can be removed)
To be on the safe side, one can isolate the virtual machine from Mac (in the security settings). I had printscreens of the following three steps, but due to my still low reputation, I can't publish them. Sorry for that
The FpLoader.img can be connected to the Floppy drive.
And finally, the boot settings can be adjusted not to loose time scanning the Hard disk for boot sectors.
I hope this description gives enough information to get you starting if you want to develop an OS using a Mac and Parallels.
Kind regards, PB