Running Mikeos on a *real* 8086

[Burik]

Well it turned out that the always trustworthy PC Hardware Book doesn't mention that the sectors per FAT on a 720Kb disk are 3 and not 9. I found out the correct value by examining the boot sector of a 720Kb DOS-formatted disk [why didn't I think of that before? I've been banging my head against the wall two days because of this].

FYI, these are the correct values for a 720Kb 3.5" disk:

Code: Select all

OEMLabel                db "MIKEBOOT"
BytesPerSector          dw 512
SectorsPerCluster       db 2            ; 1 for 1.44Mb disk
ReservedForBoot         dw 1
NumberOfFats            db 2
RootDirEntries          dw 112          ; 224 for 1.44Mb disk
LogicalSectors          dw 1440         ; 2880 for 1.44Mb disk
MediumByte              db 0F9h         ; 0F0h for 1.44Mb disk
SectorsPerFat           dw 3            ; 9 for 1.44Mb disk
SectorsPerTrack         dw 9            ; 18 for 1.44Mb disk
Sides                   dw 2
HiddenSectors           dd 0
LargeSectors            dd 0
DriveNo                 dw 0
Signature               db 41
VolumeID                dd 00000000h
VolumeLabel             db "MIKEOS     "
FileSystem              db "FAT12   "

With the above in mind I've been fiddling around a bit with the FAT driver and been able to boot the 720Kb disk in QEMU but I didn't get past the start menu due to me too lazy to check for each entry in the driver [atm I can list the floppy contents but that's it]. Anyway, booting the 8086 M24 would be a completely different matter due to the lack of the popa/pusha opcodes. I admit I lose interest in this but hey, it was worth a try and it got me the urge to write my first real-mode OS

Ciao!