Edit: So I got things working by not using Bochs from apt but compile from source. Does anyone know how they are different?
I am trying to make a bootloader that simply displays the string "hello, world" on the screen. I created a raw disk image from my assembly code, and simulated the same image with both QEMU and Bochs. QEMU successfully printed the string, while Bochs only shows a black screen (I didn't forget to type 'c' to continue the simulation on Bochs). What am I doing wrong here?
Here's my assembly code (boot.asm):
org 0x7c00
Start:
xor ax, ax
mov ds, ax
mov es, ax
mov ss, ax
mov sp, 0x7c00
mov ax, 0600h
mov bx, 0700h
mov cx, 0
mov dx, 0184fh
int 10h
mov ax, 0200h
mov bx, 0000h
mov dx, 0000h
int 10h
mov ax, 1301h
mov bx, 000fh
mov dx, 0000h
mov cx, 12
push ax
mov ax, ds
mov es, ax
pop ax
mov bp, Message
int 10h
xor ah, ah
xor dl, dl
int 13h
jmp $
Message: db "hello, world"
times 510 - ($ - $$) db 0
dw 0xaa55
Here's how I made the disk image:
$ nasm boot.asm
$ dd if=/dev/zero of=boot.img bs=512 count=2880
$ dd if=boot of=boot.img conv=notrunc
I ran QEMU with the command qemu-system-x86_64 -drive format=raw,file=boot.img, and Bochs with the following configuration:
# configuration file generated by Bochs
plugin_ctrl: unmapped=true, biosdev=true, speaker=true, extfpuirq=true, parallel=true, serial=true, gameport=true, iodebug=true
config_interface: textconfig
display_library: x
memory: host=32, guest=32
romimage: file="/usr/share/bochs/BIOS-bochs-latest", address=0x00000000, options=none
vgaromimage: file="/usr/share/bochs/VGABIOS-lgpl-latest"
boot: floppy
floppy_bootsig_check: disabled=0
floppya: type=1_44, 1_44="boot.img", status=inserted, write_protected=0
# no floppyb
ata0: enabled=true, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14
ata0-master: type=none
ata0-slave: type=none
ata1: enabled=true, ioaddr1=0x170, ioaddr2=0x370, irq=15
ata1-master: type=none
ata1-slave: type=none
ata2: enabled=false
ata3: enabled=false
optromimage1: file=none
optromimage2: file=none
optromimage3: file=none
optromimage4: file=none
optramimage1: file=none
optramimage2: file=none
optramimage3: file=none
optramimage4: file=none
pci: enabled=1, chipset=i440fx
vga: extension=vbe, update_freq=5, realtime=1
cpu: count=1:1:1, ips=4000000, quantum=16, model=bx_generic, reset_on_triple_fault=1, cpuid_limit_winnt=0, ignore_bad_msrs=1, mwait_is_nop=0
cpuid: level=6, stepping=3, model=3, family=6, vendor_string="GenuineIntel", brand_string=" Intel(R) Pentium(R) 4 CPU "
cpuid: mmx=true, apic=xapic, simd=sse2, sse4a=false, misaligned_sse=false, sep=true
cpuid: movbe=false, adx=false, aes=false, sha=false, xsave=false, xsaveopt=false, avx_f16c=false
cpuid: avx_fma=false, bmi=0, xop=false, fma4=false, tbm=false, x86_64=true, 1g_pages=false
cpuid: pcid=false, fsgsbase=false, smep=false, smap=false, mwait=true, vmx=1, svm=false
print_timestamps: enabled=0
debugger_log: -
magic_break: enabled=0
port_e9_hack: enabled=0
private_colormap: enabled=0
clock: sync=none, time0=local, rtc_sync=0
# no cmosimage
log: -
logprefix: %t%e%d
debug: action=ignore
info: action=report
error: action=report
panic: action=ask
keyboard: type=mf, serial_delay=250, paste_delay=100000, user_shortcut=none
mouse: type=ps2, enabled=false, toggle=ctrl+mbutton
sound: waveoutdrv=dummy, waveout=none, waveindrv=dummy, wavein=none, midioutdrv=dummy, midiout=none
speaker: enabled=true, mode=sound
parport1: enabled=true, file=none
parport2: enabled=false
com1: enabled=true, mode=null
com2: enabled=false
com3: enabled=false
com4: enabled=false