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237 lines
5.9 KiB
237 lines
5.9 KiB
ORG 0x600
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BITS 16
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; SLRboot
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; Bootloader for SingOS
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; version 0.3.0.0
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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cli
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;jmp long 0x0000:start
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mov ax, 0x1000
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mov ss, ax
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mov sp, 0xb000
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push dx
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mov ax, 0x0
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mov ds, ax ; ds is used by si
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mov es, ax ; es is used by di
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sti
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mov si, 0x7c00
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mov di, 0x600
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mov cx, 0x100
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rep movsw
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jmp 0x0000:relocated
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relocated:
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mov ax, 0x0
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mov ds, ax
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mov es, ax
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pop dx
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mov [disk_identifier], dl
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mov si, message ; Put address of the null-terminated string to output into 'si'
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call print ; Call our string-printing routine
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; Check for more than one active partition that we can start from.
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xor bx, bx
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xor cx, cx
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mov ax, [partition_1.active_partition]
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cmp al, 0x80
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jne check_p_2
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mov bx, 0x01 ; Partion 1 active
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inc cx
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check_p_2:
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mov ax, [partition_2.active_partition]
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cmp al, 0x80
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jne check_p_3
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inc cx
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mov bx, 0x02 ; Partion 2 active
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check_p_3:
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mov ax, [partition_3.active_partition]
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cmp al, 0x80
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jne check_p_4
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inc cx
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mov bx, 0x03 ; Partion 3 active
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check_p_4:
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mov al, [partition_4.active_partition]
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cmp ax, 0x80
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jne eval_active_partion_number
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inc cx
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mov bx, 0x04 ; Partion 4 active
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cli
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hlt
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eval_active_partion_number:
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cmp cx, 1
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je boot_partition
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; here goes wait call, for the user to enter debug mode.
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; Wating for 2 seconds:
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mov ah, 0x86 ; code for waiting interupt call
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mov cx, 0x001e ; high count of microseconds
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mov dx, 0x8480 ; low count
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int 0x15
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.busy_wait_for_key:
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xor ax, ax
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mov ah, 0x01 ; BIOS call to wait for key
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int 0x16
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boot_partition:
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; IMPORTANT bx, has to hold the value 1-4 for the partiotion that wanted to be booted.
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mov bx, 1
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mov ax, partition_1
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.loop:
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cmp bx, 1
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je break
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add ax, 0x10
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dec bx
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jmp .loop
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break:
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add ax, 8 ; This is the offset to fetch the LBA start adress of the partition record
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mov bx, ax
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xor ax, ax
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mov ax, [bx] ; first part of LBA
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mov WORD [DAPACK.lba_addr_dw_low], ax
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;call dumpax
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add bx, 2 ; next part
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mov ax, [bx]
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mov WORD [DAPACK.lba_addr_dw_low + 2], ax
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;call dumpax
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;mov WORD [DAPACK.lba_addr_dw_low], 2048
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mov WORD [DAPACK.blkcnt], 0x01
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mov WORD [DAPACK.db_addr_offset], 0x7c00
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mov WORD [DAPACK.db_addr_segment], 0x0000
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mov si, DAPACK ; address of "disk address packet"
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xor ax, ax
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mov ah, 0x42 ; READ
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mov dl, [disk_identifier]
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int 0x13
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jc endcarrycheck ; An error ocurred when reading from disk.
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; If no error then jump to volume boot record
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notcarry:
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mov dl, [disk_identifier]
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jmp long 0x0:0x7c00
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cli
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hlt
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; If we did not suceed to read from disk
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endcarrycheck:
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mov si, error_str
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call print
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cli ; Clear the Interrupt Flag (disable external interrupts)
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hlt ; Halt the CPU (until the next external interrupt)
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debug_mode:
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mov si, welcome_debug
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call print
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cli ; Clear the Interrupt Flag (disable external interrupts)
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hlt
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;Routine for printing a 'ax' as hex
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dumpax:
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pusha ; save registers
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mov bx, ax
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mov ah, 0xE ; Teletype output
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mov cx, 4 ; 4 nipples in a 16 bit word
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.loop:
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rol bx, 4 ; rotate to next nipple
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mov al, bl ; we copy to al because we need to mask only the low 4 bits
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and al, 1111b ; Do the masking
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add al, '0' ; convert to ASCII
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cmp al, '9' ; If we are greater than 9 ascii, we add 7 to make digit 10 be represented as 'A'
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jbe .skip ; -|-
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add al, 7 ; -|-
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.skip: ; -|-
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int 0x10 ; BIOS call 'output'
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loop .loop
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popa ; restore registers
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ret
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printCRLF:
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mov ah, 0xE
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mov al, 13
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int 0x10
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mov al, 10
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int 0x10
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ret
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; Routine for outputting string in 'si' register to screen
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print:
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mov ah, 0xE ; Specify 'int 0x10' 'teletype output' function
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; [AL = Character, BH = Page Number, BL = Colour (in graphics mode)]
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.printchar:
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lodsb ; Load byte at address SI into AL, and increment SI
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cmp al, 0
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je .done ; If the character is zero (NUL), stop writing the string
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int 0x10 ; Otherwise, print the character via 'int 0x10'
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jmp .printchar ; Repeat for the next character
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.done:
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ret
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data:
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message db 'SLRboot for SingOS! v0.3.0.0',13,10,0
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enter_debug_mode db 'Press d to enter bootloader debug mode',13,10,0
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welcome_debug db 'Debug mode v.0.0.1:',13,10,0
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error_str db 'Error', 0
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boot_this_partition: dw 0
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disk_identifier db 0
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DAPACK:
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.dap_Size: db 0x10 ; This is always 16 bytes (0x10)
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.rev_byte: db 0x0 ; reserved byte, should always be zero
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.blkcnt: dw 0x0 ; int 13 resets this to # of blocks actually read/written
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.db_addr_offset: dw 0x0 ; memory buffer destination address (0:7c00)
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.db_addr_segment: dw 0x0 ; in memory page zero
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.lba_addr_dw_low: dd 0x0 ; put the lba to read in this spot
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.lba_addr_dw_high: dd 0x0 ; more storage bytes only for big lba's ( > 4 bytes )
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; Pad to 510 bytes (boot sector size minus 2) with 0s, and finish with the two-byte standard boot signature
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times 446-($-$$) db 0 ; First partion entry
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partition_1:
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.active_partition db 0x80
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.start_CHS db 0x00, 0x00, 0x11;0x20, 0x21, 0x00
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.disk_type db 0x83
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.end_CHS db 0x8C, 0x3D, 0x0F
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.start_LBA db 0x10, 0x00, 0x00, 0x00
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.size db 0x00, 0xC8, 0x03, 0x00
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; sector number for 2.nd SingOS -> 16480
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partition_2:
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.active_partition db 0x80
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.start_CHS db 0x8C, 0x3E, 0x0F
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.disk_type db 0x83
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.end_CHS db 0xFF, 0xFF, 0xFF
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.start_LBA db 0x61, 0x40, 0x00, 0x00 ;0x00, 0xD0, 0x03, 0x00
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.size db 0x00, 0x28, 0x1C, 0x03
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partition_3:
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.active_partition db 0x00
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.start_CHS db 0x00, 0x00, 0x00
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.disk_type db 0x00
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.end_CHS db 0x00, 0x00, 0x00
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.start_LBA db 0x00, 0x00, 0x00, 0x00
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.size db 0x00, 0x00, 0x00, 0x00
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partition_4:
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.active_partition db 0x00
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.start_CHS db 0x00, 0x00, 0x00
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.disk_type db 0x00
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.end_CHS db 0x00, 0x00, 0x00
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.start_LBA db 0x00, 0x00, 0x00, 0x00
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.size db 0x00, 0x00, 0x00, 0x00
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times 510-($-$$) db 0
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dw 0xAA55 ; => 0x55 0xAA (little endian byte order)
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; bootloder debug_mode goes here
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times 8192-($-$$) db 0
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