Sreg yields es:0x8f60, which is a dynamically computed address right before the EBDA.Ĭomparing both, I don't see a significant difference that might influence the functioning of the interrupt routine, so the problem cannot be the parameters passed via registers.ĭoes anybody have other suggestions on what to do?Ī couple of issues with your Int 13h/AH=02h floppy disk reading code: The GPRs' content right before the int 0x13 is as follows (obtained using r in the bochs shell): CPU0: to no avail.Īs I already said before, I already loaded some sectors from disk into memory. I tried zeroing out the upper 16-bit part of eax. I figured maybe there is indeed a bug in the BIOS routine and somehow eax is used and not ax.

As a test, I altered my second stage to read sector 1 and it still didn't work.

The int 0x13 in my second stage is similar so I would have expected it to work. Maybe reading the fifth sector is somehow out of bounds or whatever? The code that uses int 0x13 to read my second stage works as expected. I thought that maybe overriding the IVT or BDA might not be a good idea during execution of a BIOS interrupt routine, so I tried loading the sector to 0圆00 ( es = 0圆0, bx = 0x0) (I know that the BDA is only 256 bytes in size). R14: 00000000_00000000 r15: 00000000_00000000Įflags 0x00007046: id vip vif ac vm rf NT IOPL=3 of df if tf sf ZF af PF cfĪh = 0x2 (routine ID), al = 0x1 (number of sectors), ch = 0x0 (lower byte of cylinder number), cl = 0x5 (sector number and high two bits of cylinder no.), dh = 0x0 (head number), dl = 0x0 (drive number).Īnd bx = 0x0, so the sector is loaded to 0x0:0x0, just as I intended. To build just use make all and then run with BOCHS using the command bochsįirst thing I did was verifying I really got all parameters right. Int $0x13 /* <- This int 0x13 doesn't seem to return */Īll of the code can be found in my Github repository. I believe the relevant code from my second stage is: bootsys_start: In the second stage of my bootloader I'm trying to load some sectors off a virtual floppy disk into memory in bochs, but upon invoking int 0x13, the routine just does not return.

Website to read floppy disk emulator