> 8го терабайта

гигабайта же.

Кстати, нахваливающим "старые добрые" я бы посоветовал просто полистать Ralf Brown's interrupt list и всю ту кучу экстеншенов и воркароундов ...  
http://www.ctyme.com/intr/int.htm
http://www.ctyme.com/intr/int-13.htm

ну или можно глянуть в код груба, там тоже "костылей обхода" вагон и маленькая тележка.
https://github.com/coreos/grub/blob/40e2f6fd353061fdb3ec4dd6...

* This is a workaround for buggy BIOSes which don't pass boot
* drive correctly. If GRUB is installed into a HDD, check if
* DL is masked correctly. If not, assume that the BIOS passed
* a bogus value and set DL to 0x80, since this is the only

https://github.com/coreos/grub/blob/40e2f6fd353061fdb3ec4dd6...

*  Determine the hard disk geometry from the BIOS!
*  We do this first, so that LS-120 IDE floppies work correctly.

https://github.com/coreos/grub/blob/40e2f6fd353061fdb3ec4dd6...

*  %dl may have been clobbered by INT 13, AH=41H.
*  This happens, for example, with AST BIOS 1.04.

https://github.com/coreos/grub/blob/40e2f6fd353061fdb3ec4dd6...

   /* Check if unsuccessful. Ignore return value if carry isn't set to 
     workaround some buggy BIOSes. */

https://github.com/coreos/grub/blob/40e2f6fd353061fdb3ec4dd6...

/* Some buggy BIOSes doesn't return the total sectors
                   correctly but returns zero. So if it is zero, compute
                   it by C/H/S returned by the LBA BIOS call.  */
                total_sectors = ((grub_uint64_t) drp->cylinders)