For some reason I will debug bios to see how it works.

Get&Build BIOS

git clone https://github.com/coreboot/seabios.git
make

Debug BIOS

Do not try x/i command in gdb when debugging bios, because gdb does not support 16 bit segmentation memory management You must provide the correct address, do not simply use x/10i, it will not work in real mode because 8086 doesn’t support flat memory model(google it) , you must provide the segment seletor and the offset, such x/10i 0xffffabcd, or 0x000fabcd, see https://stackoverflow.com/questions/62513643/qemu-gdb-does-not-show-instructions-of-firmware.

Way 1

qemu-system-i386 -bios out/bios.bin -S -s

╭─    ~/Learning/System/Linux/Kernel/seabios  on   master ?2 ········ ✔ ─╮
╰─ ls                                                                             ─╯
COPYING         docs      out     rom16offset.o  src
COPYING.LESSER  Makefile  README  scripts        vgasrc
╭─    ~/Learning/System/Linux/Kernel/seabios  on   master ?2 ········ ✔ ─╮
╰─ gdb ./out/rom.o                                                             ─╯

in gdb

target remote :1234

Way 2

See, https://stackoverflow.com/questions/49405417/how-to-launch-openbios-from-qemu.

qemu-system-i386 -L . -vga cirrus -serial stdio -S -s

# In gdb
target remote :1234