4e108bf052
value. Ignore failure to update mbr sector. Disable interrupts while using extended registers. Default to F1 not F2.
237 lines
6.4 KiB
ArmAsm
237 lines
6.4 KiB
ArmAsm
#
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# Copyright (c) 1998 Robert Nordier
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms are freely
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# permitted provided that the above copyright notice and this
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# paragraph and the following disclaimer are duplicated in all
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# such forms.
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#
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# This software is provided "AS IS" and without any express or
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# implied warranties, including, without limitation, the implied
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# warranties of merchantability and fitness for a particular
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# purpose.
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#
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# $Id: boot0.s,v 1.3 1998/10/10 14:03:03 rnordier Exp $
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# A 512-byte boot manager.
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.set LOAD,0x7c00 # Load address
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.set ORIGIN,0x600 # Relocation address
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.set PRT_OFF,0x1be # Partition table
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.set FAKE,0x810 # Partition entry
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.set MNUOPT,0x81c # Menu options
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.globl start # Entry point
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start: cld # String ops inc
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xorl %eax,%eax # Zero
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movl %eax,%es # Address
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movl %eax,%ds # data
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movl %eax,%ss # Set up
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movwir(LOAD,_sp) # stack
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movl %esp,%esi # Source
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movwir(start,_di) # Destination
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movwir(0x100,_cx) # Word count
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rep # Relocate
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movsl # code
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movb $0x10,%cl # Words to clear
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rep # Zero
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stosl # them
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incb1(-0xe,_di_) # Sector number
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jmpnwi(main-LOAD+ORIGIN) # To relocated code
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main: movbrm(_dl,FAKE) # Save drive number
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callwi(putn) # To new line
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movwir(partbl,_bx) # Partition table
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xorl %edx,%edx # Item
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main.1: movbr0(_dh,_bx_) # Mark inactive
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movb1r(0x4,_bx_,_al) # Load type
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movwir(table0,_di) # Exclusion table
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movb $0x3,%cl # Entries
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repne # Exclude
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scasb # partition?
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je main.3 # Yes
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movb $0xa,%cl # Entries
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repne # Known
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scasb # type?
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jne main.2 # No
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leaw1r(0xa,_di_,_di) # Name table
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main.2: movwir(item,_si) # Display start
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callwi(putkey) # of menu item
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movl %edi,%esi # Set pointer
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lodsb # to
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cwde # partition
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add %eax,%esi # description
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callwi(puts) # Display it
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btswrm(_dx,MNUOPT) # Flag option enabled
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main.3: addb $0x10,%bl # Next entry
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incl %edx # Next item
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cmpb $0x4,%dl # Done?
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jb main.1 # No
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movwir(prompt,_si) # Display
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callwi(putstr) # prompt
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movbmr(opt,_dl) # Display
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decl %esi # default
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callwi(putkey) # key
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xorb %ah,%ah # BIOS: Get
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int $0x1a # system time
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movl %edx,%edi # Save
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main.4: movb $0x1,%ah # BIOS: Check
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int $0x16 # for keypress
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jnz main.6 # Have one
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xorb %ah,%ah # BIOS: Get
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int $0x1a # system time
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subl %edi,%edx # Elapsed time
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cmpwmr(ticks,_dx) # Timeout?
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jb main.4 # No
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jmp main.7 # Join common code
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main.5: movb $0x7,%al # Signal
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callwi(putchr) # error
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main.6: xorb %ah,%ah # BIOS: Get
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int $0x16 # keypress
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movb %ah,%al # Scan code
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cmpb $0x1c,%al # Enter pressed?
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jne main.8 # No
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main.7: movbma(opt) # Load
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jmp main.9 # default
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main.8: subb $0x3b,%al # Less F1 scan code
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jb main.5 # Not a function key
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main.9: cmpb $0x4,%al # F1..F5?
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ja main.5 # No
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movwir(FAKE,_si) # Partition entry
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movb0r(_si_,_dl) # Load drive number
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jne main.10 # If not F5
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xorb $0x1,%dl # Toggle drive
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jmp main.11 # number
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main.10: cwtl # Option
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btwrm(_ax,MNUOPT) # enabled?
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jnc main.5 # No
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movbam(opt) # Save option
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shlb $0x4,%al # Point to
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addwia(partbl) # partition
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xchgl %esi,%eax # entry
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movbi0(0x80,_si_) # Flag active
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pushl %esi # Save
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movl %eax,%esi # Fake partition entry
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movwir(start,_bx) # Data to write
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movwir(0x301,_ax) # Write sector
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callwi(intx13) # to disk
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popl %esi # Restore
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main.11: movwir(LOAD,_bx) # Address for read
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movwir(0x201,_ax) # Read sector
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callwi(intx13) # from disk
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jc main.5 # If error
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cmpwi2(0xaa55,0x1fe,_bx_) # Bootable?
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jne main.5 # No
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movwir(crlf,_si) # Leave some
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callwi(puts) # space
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jmp *%ebx # Invoke bootstrap
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# Display routines
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putkey: movb $'F',%al # Display
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callwi(putchr) # 'F'
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movb $'1',%al # Prepare
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addb %dl,%al # digit
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jmp putstr.1 # Display the rest
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puts: callwi(putstr) # Display string
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putn: movwir(crlf,_si) # To next line
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putstr: lodsb # Get byte
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testb $0x80,%al # End of string?
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jnz putstr.2 # Yes
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putstr.1: callwi(putchr) # Display char
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jmp putstr # Continue
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putstr.2: andb $~0x80,%al # Clear MSB
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putchr: pushl %ebx # Save
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movwir(0x7,_bx) # Page:attribute
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movb $0xe,%ah # BIOS: Display
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int $0x10 # character
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popl %ebx # Restore
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ret # To caller
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# Disk I/O
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intx13: cli # Disable interrupts
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movb1r(0x1,_si_,_dh) # Load head
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movw1r(0x2,_si_,_cx) # Load cylinder:sector
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o16 # Load
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movw1r(0x8,_si_,_di) # offset
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movwir(break,_si) # Packet pointer
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movbi0(0x10,_si_) # Packet size
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movbr1(_al,0x2,_si_) # Block count
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movwr1(_bx,0x4,_si_) # Transfer
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movws1(_es,0x6,_si_) # buffer
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o16 # LBA
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movwr1(_di,0x8,_si_) # address
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sti # Enable interrupts
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tstbim(0x80,flags) # Try for extensions?
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jz intx13.2 # No
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pushl %ecx # Save
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pushl %ebx # caller's
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movwir(0x55aa,_bx) # Magic
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pushl %eax # Save
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movb $0x41,%ah # BIOS: EDD extensions
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int $0x13 # present?
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popl %eax # Restore
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jc intx13.1 # No
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cmpwir(0xaa55,_bx) # Magic?
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jne intx13.1 # No
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testb $0x1,%cl # Use packet?
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jz intx13.1 # No
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orb $0x40,%ah # Use EDD
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intx13.1: popl %ebx # Restore
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popl %ecx # caller's
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testb $0x40,%ah # Use EDD?
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jz intx13.2 # No
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xorb %al,%al # Verify off
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intx13.2: int $0x13 # BIOS: Disk I/O
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ret # To caller
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# Menu strings
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crlf: .ascii "\r"; .byte '\n'|0x80
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item: .ascii " "; .byte ' '|0x80
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prompt: .ascii "\nDefault:"; .byte ' '|0x80
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# Partition type tables
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table0: .byte 0x0, 0x5, 0xf
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table1: .byte 0x1, 0x4, 0x6, 0xb, 0xc, 0xe, 0x63, 0x83
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.byte 0xa5, 0xa6
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.byte os_misc-.-1 # Unknown
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.byte os_dos-.-1 # DOS
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.byte os_dos-.-1 # DOS
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.byte os_dos-.-1 # DOS
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.byte os_dos-.-1 # Windows
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.byte os_dos-.-1 # Windows
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.byte os_dos-.-1 # Windows
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.byte os_unix-.-1 # UNIX
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.byte os_linux-.-1 # Linux
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.byte os_freebsd-.-1 # FreeBSD
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.byte os_bsd-.-1 # OpenBSD
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os_misc: .ascii "?"; .byte '?'|0x80
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os_dos: .ascii "DO"; .byte 'S'|0x80
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os_unix: .ascii "UNI"; .byte 'X'|0x80
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os_linux: .ascii "Linu"; .byte 'x'|0x80
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os_freebsd: .ascii "Free"
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os_bsd: .ascii "BS"; .byte 'D'|0x80
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.org PRT_OFF-0x4,0x90
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opt: .byte 0x0 # Option
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flags: .byte FLAGS # Flags
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ticks: .word TICKS # Delay
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partbl: .fill 0x40,0x1,0x0 # Partition table
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.word 0xaa55 # Magic number
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break: # Uninitialized data
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