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!
! This floppy bootblock bypasses the floppy boot ...
!
BOOTDISK = 0x80
ORGADDR = $0600
use16
org ORGADDR
start:
include sysboot.s
org dos_sysid
.ascii "BOOT C" ! System ID
org codestart
cli ! Assume _nothing_!
cld
mov bx,#$7C00 ! Pointer to start of BB.
xor ax,ax ! Segs all to zero
mov ds,ax
mov es,ax
mov ss,ax
mov sp,bx ! SP Just below BB
mov cx,#$100 ! Move 256 words
mov si,bx ! From default BB
mov di,#ORGADDR ! To the correct address.
rep
movsw
jmpi cont,#0 ! Set CS:IP correct.
cont:
sti ! Let the interrupts back in.
mov si,#mesg
call prtmsg
mov di,#5
hcode:
mov bx,#$7C00 ! Pointer to start of BB.
mov ax,#$0201 ! Read 1 sector
mov cx,#$0001 ! From sector 1
mov dx,#BOOTDISK ! Of the hard drive head zero
int $13
jc error
jmpi $7c00,0
error:
mov si,#mesg2
call prtmsg
dec di
jz reboot
mov si,#mesg3
call prtmsg
jmp hcode
prtmsg:
lodsb
cmp al,#0
jz EOS
mov bx,#7
mov ah,#$E ! Can't use $13 cause that's AT+ only!
int $10
jmp prtmsg
EOS:
ret
reboot:
mov si,#mesg4
call prtmsg
xor ax,ax
int $16
jmpi $0,$FFFF ! Reboot.
mesg2: .asciz "Disk error\r\n"
mesg3: .asciz "Retrying\r\n"
mesg4: .asciz "Press a key:"
export mesg
if BOOTDISK = 0x80
mesg: .asciz "Bypassing floppy boot\r\n"
else
mesg: .asciz "Booting drive two\r\n"
endif
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