IMG file

[david]

bochs can make hd img file,
in the img file
the first sector is from 0 to 0x1FF, the second sector is from 0x200 to 0x3FF, the third sector is from 0x400 to 0x5FF,
...... etc.
am i right?

[Troy Martin]

Yep.

post++;

[david]

Code: Select all

# hard disk
ata0: enabled=1, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14
ata0-master: type=disk, path="c.img", mode=flat, cylinders=20, heads=16, spt=63

the cylinders. heads and spt decide the size of hd img file.
I can creat a file, size is 10,321,920 bytes, named 'c.img', then i can make this file as the hd img file to use.
am i right?

[david]

another question: bochs can not read/write hd via LBA ?

Code: Select all

; LBA
	mov ax, 4200h
	mov dl, 80h
	mov si, offset cs:dap
	push cs
	pop ds
	int 13h

	jmp $

dap:	db	10h
		db	0
		dw	5
		dw	0	
		dw	3000h
		dd	0
		dd	0

when i debug the code, bochs told me that:

Code: Select all

>>PANIC<< int13_harddisk: function 42. Can't use 64bits lba

[jal]

when i debug the code, bochs told me that:

Code: Select all

>>PANIC<< int13_harddisk: function 42. Can't use 64bits lba

Thanks for letting us know. Is there a question?


JAL

[captainwiggles]

bochs works with 28 bit LBA, but not 48 bit, and I didn't even know 64 bit LBA existed :\

[Troy Martin]

and I didn't even know 64 bit LBA existed :\

Me neither, and I've been at this for almost a year You learn new things every day.





Ooohhhhh, so that's why we have school....

[quok]

bochs works with 28 bit LBA, but not 48 bit, and I didn't even know 64 bit LBA existed :\

Bochs 2.3.7 (perhaps 2.3.5, I'm not sure) works fine with 48-bit LBA. It's in the Changelog for one of the two versions.

[JohnnyTheDon]

The 64-bit LBA eror is because the upper bits of the LBA address you're sending has something other than 0s in it. Somewhere the LBA address is getting corrupted, either in your DAP or when you generate the address.

[david]

I use Bochs 2.3.5

[david]

my error, i forgot the cs's value is 0 when bochs jmps to 0x7c00.

it's ok now.

Code: Select all

; set CS=07C0, IP=@F
	push 07C0h
	push @F
	retf
@@:	

; LBA
	mov ax, 4200h
	mov dl, 80h
	mov si, offset cs:dap
	push cs
	pop ds
	int 13h

dap:	db	10h
		db	0
		dw	5
		dw	0	
		dw	3000h
		dd	0
		dd	0

[Troy Martin]

Instead of this:

Code: Select all

; set CS=07C0, IP=@F
	push 07C0h
	push @F
	retf
@@:

You should probably do this:

Code: Select all

; set CS = 07C0h, IP = after this jump
	jmp 0x07C0:sync

sync:

Saves a byte IIRC. And in a bootloader, a byte saved is both a byte earned AND a seriously important thing.