i386/boot1/nullboot1.asm

   1 ; bootnot.asm - boot1 written for turbo assembler, since gas only
   2 ; generates 32 bit code and this must run in real mode.
   3 ; To compile as floppy boot1f.not:
   4 ;       tasm /m3 /dBOOTDEV=FLOPPY boot1 ,boot1f
   5 ;       tlink boot1f
   6 ;       exe2bin boot1f
   7 ;       ren boot1f.bin boot1f.not
   8
   9 ;***********************************************************************
  10 ;       This is the code for the NeXT boot1 bootsector.
  11 ;***********************************************************************
  12
  13         P486                    ;enable i386 instructions
  14         IDEAL
  15         SEGMENT CSEG
  16         ASSUME CS:CSEG,DS:CSEG
  17
  18         SDEBUG = 0
  19
  20 ;BOOTSEG                =       100h    ; boot will be loaded at 4k
  21 ;BOOTOFF                =       0000h
  22 BOOTSEG         =       00h
  23 BOOTOFF         =       1000h
  24 BUFSZ           =       2000h   ; 8K disk transfer buffer
  25
  26 ; This code is a replacement for boot1.  It is loaded at 0x0:0x7c00
  27
  28 start:
  29         mov     ax,BOOTSEG
  30         cli                     ; interrupts off
  31         mov     ss,ax           ; set up stack seg
  32         mov     sp,0fff0h
  33         sti                     ; reenable interrupts
  34
  35         xor     ax,ax
  36         mov     es,ax
  37         mov     ds,ax
  38         mov     si,7C00h
  39         cld                     ; so pointers will get updated
  40         mov     di,0E000h       ; relocate boot program to 0xE000
  41         mov     cx,100h         ; copy 256x2 bytes
  42         repnz   movsw           ; move it
  43         off1    =  0E000h + (a1 - start)
  44         jmp     FAR 0000:off1   ; jump to a1 in relocated place
  45
  46 a1:
  47         mov     ax,0E00h
  48         mov     ds,ax
  49         mov     ax,BOOTSEG
  50         mov     es,ax
  51
  52         mov     si, OFFSET not_boot
  53         call    message         ; display intro message
  54
  55 halt:
  56         mov     ah, 00h
  57         int     16h
  58         jmp     halt            ; get key and loop forever
  59
  60 message:                                ; write the error message in ds:esi
  61                                         ; to console
  62         push    es
  63         mov     ax,ds
  64         mov     es,ax
  65
  66         mov     bx, 1                   ; bh=0, bl=1 (blue)
  67         cld
  68
  69 nextb:
  70         lodsb                           ; load a byte into al
  71         cmp     al, 0
  72         je      done
  73         mov     ah, 0eh                 ; bios int 10, function 0xe
  74         int     10h                     ; bios display a byte in tty mode
  75         jmp     nextb
  76 done:   pop     es
  77         ret
  78
  79 putchr:
  80         push    bx
  81         mov     bx, 1                   ; bh=0, bl=1 (blue)
  82         mov     ah, 0eh                 ; bios int 10, function 0xe
  83         int     10h                     ; bios display a byte in tty mode
  84         pop     bx
  85         ret
  86
  87
  88 not_boot:
  89         db      10,13
  90         db     'The disk in the floppy disk drive isn''t a startup disk:'
  91         db      10,13
  92         db      'It doesn''t contain '
  93         db      'the system files required to start up the computer.'
  94         db      10,13
  95         db      'Please eject this disk and restart the computer'
  96         db      ' with a floppy disk,'
  97         db      10,13
  98         db      'hard disk, or CD-ROM that is a startup disk.'
  99         db      10,13
 100         db      0
 101
 102 ; the last 2 bytes in the sector contain the signature
 103 d1:
 104         a2 = 510 - (d1 - start)
 105         DB a2 dup (0)
 106         DW 0AA55h
 107         ENDS
 108         END