You need to build a coreboot image for QEMU with SeaBIOS (master)
selected as the default payload. CBFS size should be increased to a
size large enough to contain your floppy (or floppies, btw here's a
patch to support multiple floppies at CBFS -
https://review.coreboot.org/c/coreboot/+/32238 , and you could install
it with this script - https://pastebin.com/raw/hv9sSuMU , more details
here - https://mail.coreboot.org/hyperkitty/list/seabios@seabios.org/thread/CKWLNTZU43SAHQ26USNFASORA2H5BXBE/
) . After it will be compiled, you could use cbfstool to add/remove
floppies to/from CBFS of coreboot.rom, with LZMA compression to reduce
their size:
1) Add: ./build/cbfstool ./build/coreboot.rom add -f
./path_to/myfloppy.img -n floppyimg/myfloppy.lzma -t raw -c lzma
2) Remove (e.g. to add a new version later): ./build/cbfstool
./build/coreboot.rom remove -n floppyimg/myfloppy.lzma
3) Print a memory map: ./build/cbfstool ./build/coreboot.rom print
Run this coreboot.rom by executing this QEMU command: (some floppies are 64-bit)
qemu-system-x86_64 -L . -m 768 -localtime -vga vmware -net nic,model=rtl8139 \
 -net user -soundhw ac97 -bios ./coreboot.rom -boot menu=on -serial stdio
Best regards,
Mike Banon

On Mon, Apr 15, 2019 at 6:12 PM Rafael Send <flyingfishfinger@gmail.com> wrote:
>
> I haven't gotten around to poking at SeaBIOS yet, I'm still wondering how to test my large floppies.
>
> Syslinux appears to install to them fine, but QEMU doesn't seem to like booting them with -fda.
>
> Do you guys have any suggestions on how to test booting the large floppy images?
>
> Cheers,
> R
>
>
>
> Mike Banon <mikebdp2@gmail.com> schrieb am Mo., 15. Apr. 2019, 05:35:
>>
>> Personally I think that either this guy did something incorrectly or
>> there's a Windows 3.1 bug. Meanwhile, Rafael's Linux-based OS is going
>> to boot from this floppy like it's a ramdisk, so hopefully should be
>> indifferent to the custom floppy sizes and would work. I share the
>> same hopes for KolibriOS: although its' 1.44MB floppy contains really
>> a LOT of stuff, some cool things like console emulators didn't fit -
>> so I'm going to create the extended Kolibri floppy version, which will
>> be either 2.88MB or some custom ( 1.44MB * X ) size.
>>
>> On Sun, Apr 14, 2019 at 6:12 PM Kevin O'Connor <kevin@koconnor.net> wrote:
>> >
>> > On Fri, Apr 12, 2019 at 11:38:52AM -0700, Rafael Send wrote:
>> > > Hi,
>> > > I'm working on stuffing a bootable Linux distro into coreboot.  In QEMU I
>> > > already succeded by using coreboot's built-in kernel loading mechanism, but
>> > > that's without SeaBIOS.
>> > >
>> > > I'd love to have it as a SeaBIOS payload so I can also boot other things,
>> > > but I guess I'd have to create a custom-sized floppy image for this or
>> > > figure out how to create an ELF payload out of a Linux kernel (I'm open to
>> > > either, but I wasn't able to find any documentation on the ELF method).
>> > >
>> > > The guy who put Win 3.1 in coreboot attempted the floppy method, but
>> > > according to his article he did not find success with this method due to
>> > > unknown and complex issues in the floppy-side logic of SeaBIOS.
>> > >
>> > > So, I'm making the question explicit: What would it take to support
>> > > custom-sized floppy images? In particular, I'm thinking of a 16MB device...
>> >
>> > My vague recollection is that various OSes had hard coded expectations
>> > on the types of floppy drives supported.  I did not think it would be
>> > easy to support a floppy size larger than 2.8MB.
>> >
>> > It is possible to emulate a hard drive in memory.  However, that would
>> > require code changes.
>> >
>> > Cheers,
>> > -Kevin
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