1 | ; Project name : XTIDE Universal BIOS
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2 | ; Description : Int 19h Handler (Boot Loader).
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3 |
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4 | ;
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5 | ; XTIDE Universal BIOS and Associated Tools
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6 | ; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2013 by XTIDE Universal BIOS Team.
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7 | ;
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8 | ; This program is free software; you can redistribute it and/or modify
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9 | ; it under the terms of the GNU General Public License as published by
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10 | ; the Free Software Foundation; either version 2 of the License, or
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11 | ; (at your option) any later version.
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12 | ;
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13 | ; This program is distributed in the hope that it will be useful,
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14 | ; but WITHOUT ANY WARRANTY; without even the implied warranty of
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15 | ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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16 | ; GNU General Public License for more details.
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17 | ; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
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18 | ;
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19 |
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20 | ; Section containing code
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21 | SECTION .text
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22 |
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23 | ;--------------------------------------------------------------------
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24 | ; Int19h_BootLoaderHandler
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25 | ; Parameters:
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26 | ; Nothing
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27 | ; Returns:
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28 | ; Never returns (loads operating system)
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29 | ;--------------------------------------------------------------------
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30 | Int19h_BootLoaderHandler:
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31 | sti ; Enable interrupts
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32 | cld ; String instructions to increment pointers
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33 | LOAD_BDA_SEGMENT_TO es, ax ; Load BDA segment (zero) to ES
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34 | ; Fall to .PrepareBootLoaderStack
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35 |
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36 |
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37 | ;--------------------------------------------------------------------
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38 | ; Drive detection and boot menu use lots of stack so it is
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39 | ; wise to relocate stack. Otherwise something important from
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40 | ; interrupt vectors are likely corrupted, likely our own DPTs if
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41 | ; they are located to 30:0h.
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42 | ;
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43 | ; .PrepareBootLoaderStack
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44 | ; Parameters:
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45 | ; ES: BDA and interrupt vector segment (zero)
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46 | ; Returns:
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47 | ; Never returns (loads operating system)
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48 | ;--------------------------------------------------------------------
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49 | .PrepareBootLoaderStack:
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50 | STORE_POST_STACK_POINTER
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51 | SWITCH_TO_BOOT_MENU_STACK
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52 | ; Fall to .InitializeDisplay
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53 |
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54 |
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55 | ;--------------------------------------------------------------------
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56 | ; .InitializeDisplay
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57 | ; Parameters:
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58 | ; ES: BDA and interrupt vector segment (zero)
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59 | ; Returns:
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60 | ; Never returns (loads operating system)
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61 | ;--------------------------------------------------------------------
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62 | .InitializeDisplay:
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63 | ; Change display mode if necessary
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64 | mov ax, [cs:ROMVARS.wDisplayMode] ; AH 00h = Set Video Mode
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65 | cmp al, DEFAULT_TEXT_MODE
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66 | je SHORT .InitializeDisplayLibrary
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67 | int BIOS_VIDEO_INTERRUPT_10h
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68 | .InitializeDisplayLibrary:
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69 | call DetectPrint_InitializeDisplayContext
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70 | ; Fall to .InitializeBiosAndDetectDrives
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71 |
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72 |
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73 | ;--------------------------------------------------------------------
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74 | ; .InitializeBiosAndDetectDrives
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75 | ; Parameters:
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76 | ; ES: BDA and interrupt vector segment (zero)
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77 | ; Returns:
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78 | ; DS: RAMVARS segment
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79 | ;--------------------------------------------------------------------
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80 | %ifdef MODULE_HOTKEYS
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81 | call TimerTicks_ReadFromBdaToAX
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82 | mov [es:BOOTVARS.hotkeyVars+HOTKEYVARS.wTimeWhenDisplayed], ax
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83 | %endif
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84 |
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85 | call Initialize_AndDetectDrives
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86 |
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87 | %ifdef MODULE_HOTKEYS
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88 | .WaitUntilTimeToCloseHotkeyBar:
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89 | call TimerTicks_ReadFromBdaToAX
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90 | sub ax, [es:BOOTVARS.hotkeyVars+HOTKEYVARS.wTimeWhenDisplayed]
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91 | cmp ax, MIN_TIME_TO_DISPLAY_HOTKEY_BAR
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92 | jb SHORT .WaitUntilTimeToCloseHotkeyBar
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93 | %endif
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94 | ; Fall to SelectDriveToBootFrom
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95 |
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96 |
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97 | ;--------------------------------------------------------------------
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98 | ; SelectDriveToBootFrom
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99 | ; Parameters:
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100 | ; DS: RAMVARS segment
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101 | ; ES: BDA and interrupt vector segment (zero)
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102 | ; Returns:
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103 | ; Never returns (loads operating system)
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104 | ;--------------------------------------------------------------------
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105 | ; The following macro could be easily inlined below. Why a macro? Depending on the combination
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106 | ; of MODULE_HOTKEYS or MODULE_BOOT_MENU, this code needs to either come before or after the
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107 | ; call to the boot menu.
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108 | ;
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109 | %macro TRY_TO_BOOT_DL_AND_DH_DRIVES 0
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110 | push dx ; it's OK if this is left on the stack, if we are
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111 | ; successful, the following call does not return
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112 | call BootSector_TryToLoadFromDriveDL_AndBoot
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113 | pop dx
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114 | mov dl, dh
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115 | call BootSector_TryToLoadFromDriveDL_AndBoot
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116 | %endmacro
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117 |
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118 |
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119 | SelectDriveToBootFrom: ; Function starts here
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120 | %ifdef MODULE_HOTKEYS
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121 | call HotkeyBar_UpdateDuringDriveDetection
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122 | mov al, [es:BOOTVARS.hotkeyVars+HOTKEYVARS.bScancode]
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123 | cmp al, ROM_BOOT_HOTKEY_SCANCODE
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124 | je SHORT .RomBoot ; CF clear so ROM boot
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125 | %ifdef MODULE_BOOT_MENU
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126 | cmp al, BOOT_MENU_HOTKEY_SCANCODE
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127 | je SHORT .BootMenu
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128 | %endif ; MODULE_BOOT_MENU
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129 |
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130 | .TryUsingHotKeysCode:
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131 | call HotkeyBar_GetBootDriveNumbersToDX
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132 | call DriveXlate_SetDriveToSwap ; Enable primary boot device translation
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133 | xchg dl, dh
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134 | call DriveXlate_SetDriveToSwap ; Enable secondary boot device translation
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135 | xchg dl, dh
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136 | call DriveXlate_ToOrBack ; Translate now so boot device will appear as 00h or 80h to OS
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137 | TRY_TO_BOOT_DL_AND_DH_DRIVES
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138 | ;; falls through to boot menu, if it is present. If not present, falls through to rom boot.
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139 | %endif ; MODULE_HOTKEYS
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140 |
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141 |
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142 | %ifdef MODULE_BOOT_MENU
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143 | .BootMenu:
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144 | call BootMenu_DisplayAndReturnDriveInDLRomBootClearCF
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145 | jnc SHORT .RomBoot ; CF clear so ROM boot
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146 |
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147 | call DriveXlate_Reset
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148 | %ifdef MODULE_HOTKEYS
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149 | jmp SHORT .TryUsingHotKeysCode ; Selected drive stored as hotkey
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150 | %else ; Boot menu without hotkeys, secondary boot drive is always 00h or 80h
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151 | mov dh, dl ; Setup for secondary drive
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152 | not dh ; Floppy goes to HD, or vice versa
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153 | and dh, 80h ; Go to first drive of the floppy or HD set
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154 | call DriveXlate_SetDriveToSwap
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155 | call DriveXlate_ToOrBack
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156 | TRY_TO_BOOT_DL_AND_DH_DRIVES
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157 | jmp SHORT .BootMenu ; Show boot menu again
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158 | %endif ; MODULE_HOTKEYS
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159 |
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160 | %endif ; MODULE_BOOT_MENU
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161 |
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162 | ; No hotkeys and no boot menu means fixed "A then C" boot order
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163 | %ifndef MODULE_HOTKEYS OR MODULE_BOOT_MENU
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164 | xor dl, dl ; Try to boot from Floppy Drive A
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165 | call BootSector_TryToLoadFromDriveDL_AndBoot
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166 | mov dl, 80h ; Try to boot from Hard Drive C
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167 | call BootSector_TryToLoadFromDriveDL_AndBoot
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168 | %endif
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169 |
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170 | .RomBoot:
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171 | %ifdef MODULE_DRIVEXLATE
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172 | call DriveXlate_Reset ; Clean up any drive mappings before Rom Boot
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173 | %endif
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174 | clc
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175 | ;; fall through to Int19_JumpToBootSectorOrRomBoot
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176 |
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177 | ;--------------------------------------------------------------------
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178 | ; Int19_JumpToBootSectorOrRomBoot
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179 | ;
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180 | ; Switches back to the POST stack, clears the DS and ES registers,
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181 | ; and either jumps to the MBR (Master Boot Record) that was just read,
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182 | ; or calls the ROM's boot routine on interrupt 18.
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183 | ;
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184 | ; Parameters:
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185 | ; DL: Drive to boot from (translated, 00h or 80h)
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186 | ; CF: Set for Boot Sector Boot
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187 | ; Clear for ROM Boot
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188 | ; ES:BX: (if CF set) Ptr to boot sector
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189 | ;
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190 | ; Returns:
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191 | ; Never returns
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192 | ;--------------------------------------------------------------------
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193 | Int19_JumpToBootSectorOrRomBoot:
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194 | mov cx, es ; Preserve MBR segment (can't push because of stack change)
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195 | mov ax, 0 ; NOTE: can't use XOR (LOAD_BDA_SEGMENT_TO) as it impacts CF
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196 | SWITCH_BACK_TO_POST_STACK
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197 |
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198 | ; clear segment registers before boot sector or rom call
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199 | mov ds, ax
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200 | mov es, ax
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201 | %ifdef USE_386
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202 | mov fs, ax
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203 | mov gs, ax
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204 | %endif
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205 | jnc SHORT .romboot
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206 |
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207 | ; jump to boot sector
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208 | push cx ; sgment address for MBR
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209 | push bx ; offset address for MBR
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210 | retf ; NOTE: DL is set to the drive number
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211 |
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212 | ; Boot by calling INT 18h (ROM Basic of ROM DOS)
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213 | .romboot:
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214 | int BIOS_BOOT_FAILURE_INTERRUPT_18h ; Never returns
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