Non system disk error

Pyrofan1 · Post by **Pyrofan1** » Fri Mar 28, 2008 12:24 pm

okay, so i'm trying to create my own bootloader
i have this code

[BITS 16]	 ; 16 bit code generation
[ORG 0x7C00]	 ; ORGin location is 7C00

;Main program
main:		 ; Main program label
jmp main		 ; Put it into a coninuous loop to stop it running off into
		 ;  the memory running any junk it may find there.

; End matter
times 510-($-$$) db 0	; Fill the rest of the sector with zeros
dw 0xAA55		; Boot signature

and use
this script to assemble and put on a floppy

Code: Select all

nasm bootloader.s -f bin -o bootloader.bin
sudo dd if=bootloader.bin bs=512 count=1 of=/dev/fd0

but when i try to boot from the floppy i get "Non-System disk or disk error"

omegaman · Post by **omegaman** » Fri Mar 28, 2008 12:56 pm

I haven't looked for flaws in the dd statement, etc, but I would suggest you do a "sync" after the dd command.

Pyrofan1 · Post by **Pyrofan1** » Fri Mar 28, 2008 1:15 pm

sync didn't help

jzgriffin · Post by **jzgriffin** » Fri Mar 28, 2008 1:31 pm

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nasm bootloader.s -f bin -o bootloader.bin
dd if=/dev/zero of=floppy.img bs=512 count=2880
dd if=bootloader.bin of=floppy.img conv=notrunc
sudo dd if=floppy.img of=/dev/fd0 bs=512

Try that.

Pyrofan1 · Post by **Pyrofan1** » Fri Mar 28, 2008 4:26 pm

That didn't work

Masterkiller · Post by **Masterkiller** » Fri Mar 28, 2008 4:47 pm

BIOS should boot at 0x07C0:0x0000, not 0x0000:0x7C00 which makes the orign of the program 0.

jzgriffin · Post by **jzgriffin** » Fri Mar 28, 2008 6:30 pm

I use ORG 0x7C00 in my bootsector and it works just fine. However, you could also do this:

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USE16
ORG 0x0000
JMP SHORT START

START:
MOV AX, 0x07C0
MOV DS, AX
MOV ES, AX
MOV FS, AX
MOV GS, AX
MOV SS, AX
MOV SP, 0x7C00 ; forgive me if this is wrong, I can never remember what to set sp to
JMP SHORT $

TIMES 510 - ($ - $$) DB 0x00
DW 0xAA55

(note: fasm syntax; replace USE16 with BITS 16 for nasm)

Also, could you do this, please?

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dd if=/dev/fd0 of=fd0.img
hexdump fd0.img

And then post the output.

One last thing, try writing to the floppy without bs=512.

Pyrofan1 · Post by **Pyrofan1** » Sat Mar 29, 2008 11:42 am

One last thing, try writing to the floppy without bs=512.

already tried it

And then post the output.

0000000 c0b8 8e07 8ed8 8ec0 8ee0 8ee8 bcd0 7c00
0000010 eeeb 0000 0000 0000 0000 0000 0000 0000
0000020 0000 0000 0000 0000 0000 0000 0000 0000
*
00001f0 0000 0000 0000 0000 0000 0000 0000 aa55
0000200 0000 0000 0000 0000 0000 0000 0000 0000
*
0168000

jzgriffin · Post by **jzgriffin** » Sat Mar 29, 2008 12:15 pm

Are you booting the floppy physically or in an emulator? If emulator, post the command / configuration.

Pyrofan1 · Post by **Pyrofan1** » Sat Mar 29, 2008 12:37 pm

physically

jzgriffin · Post by **jzgriffin** » Sat Mar 29, 2008 12:38 pm

Try booting it in QEMU:

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qemu -fda floppy.img -boot a -m 4 -no-kqemu -localtime

Pyrofan1 · Post by **Pyrofan1** » Sat Mar 29, 2008 12:50 pm

it works fine in qemu

jzgriffin · Post by **jzgriffin** » Sat Mar 29, 2008 1:19 pm

Is your floppy disk and floppy drive bad?

Pyrofan1 · Post by **Pyrofan1** » Sat Mar 29, 2008 1:32 pm

Brynet-Inc · Post by **Brynet-Inc** » Sat Mar 29, 2008 3:09 pm

Pyrofan1 wrote:No

Stop waisting everyones time, clearly the problem is on your end..