| 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 | ; Last hard drive might have scrolled Hotkey Bar out of screen.
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| 89 | ; We want to display it during wait.
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| 90 | call HotkeyBar_UpdateDuringDriveDetection
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| 91 |
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| 92 | .WaitUntilTimeToCloseHotkeyBar:
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| 93 | call TimerTicks_ReadFromBdaToAX
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| 94 | sub ax, [es:BOOTVARS.hotkeyVars+HOTKEYVARS.wTimeWhenDisplayed]
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| 95 | cmp ax, MIN_TIME_TO_DISPLAY_HOTKEY_BAR
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| 96 | jb SHORT .WaitUntilTimeToCloseHotkeyBar
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| 97 | %endif
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| 98 | ; Fall to SelectDriveToBootFrom
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| 99 |
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| 100 |
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| 101 | ;--------------------------------------------------------------------
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| 102 | ; SelectDriveToBootFrom
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| 103 | ; Parameters:
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| 104 | ; DS: RAMVARS segment
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| 105 | ; ES: BDA and interrupt vector segment (zero)
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| 106 | ; Returns:
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| 107 | ; Never returns (loads operating system)
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| 108 | ;--------------------------------------------------------------------
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| 109 | ; The following macro could be easily inlined below. Why a macro? Depending on the combination
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| 110 | ; of MODULE_HOTKEYS or MODULE_BOOT_MENU, this code needs to either come before or after the
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| 111 | ; call to the boot menu.
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| 112 | ;
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| 113 | %macro TRY_TO_BOOT_DL_AND_DH_DRIVES 0
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| 114 | push dx ; it's OK if this is left on the stack, if we are
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| 115 | ; successful, the following call does not return
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| 116 | call BootSector_TryToLoadFromDriveDL_AndBoot
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| 117 | pop dx
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| 118 | mov dl, dh
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| 119 | call BootSector_TryToLoadFromDriveDL_AndBoot
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| 120 | %endmacro
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| 121 |
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| 122 |
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| 123 | SelectDriveToBootFrom: ; Function starts here
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| 124 | %ifdef MODULE_HOTKEYS
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| 125 | call HotkeyBar_UpdateDuringDriveDetection
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| 126 | mov al, [es:BOOTVARS.hotkeyVars+HOTKEYVARS.bScancode]
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| 127 | cmp al, ROM_BOOT_HOTKEY_SCANCODE
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| 128 | je SHORT .RomBoot ; CF clear so ROM boot
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| 129 | %ifdef MODULE_BOOT_MENU
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| 130 | cmp al, BOOT_MENU_HOTKEY_SCANCODE
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| 131 | je SHORT .BootMenu
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| 132 | %endif ; MODULE_BOOT_MENU
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| 133 |
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| 134 | .TryUsingHotKeysCode:
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| 135 | call HotkeyBar_GetBootDriveNumbersToDX
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| 136 | call DriveXlate_SetDriveToSwap ; Enable primary boot device translation
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| 137 | xchg dl, dh
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| 138 | call DriveXlate_SetDriveToSwap ; Enable secondary boot device translation
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| 139 | xchg dl, dh
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| 140 | call DriveXlate_ToOrBack ; Translate now so boot device will appear as 00h or 80h to OS
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| 141 | TRY_TO_BOOT_DL_AND_DH_DRIVES
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| 142 | ;; falls through to boot menu, if it is present. If not present, falls through to rom boot.
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| 143 | %endif ; MODULE_HOTKEYS
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| 144 |
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| 145 |
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| 146 | %ifdef MODULE_BOOT_MENU
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| 147 | .BootMenu:
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| 148 | call BootMenu_DisplayAndReturnDriveInDLRomBootClearCF
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| 149 | jnc SHORT .RomBoot ; CF clear so ROM boot
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| 150 |
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| 151 | call DriveXlate_Reset
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| 152 | %ifdef MODULE_HOTKEYS
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| 153 | jmp SHORT .TryUsingHotKeysCode ; Selected drive stored as hotkey
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| 154 | %else ; Boot menu without hotkeys, secondary boot drive is always 00h or 80h
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| 155 | mov dh, dl ; Setup for secondary drive
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| 156 | not dh ; Floppy goes to HD, or vice versa
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| 157 | and dh, 80h ; Go to first drive of the floppy or HD set
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| 158 | call DriveXlate_SetDriveToSwap
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| 159 | call DriveXlate_ToOrBack
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| 160 | TRY_TO_BOOT_DL_AND_DH_DRIVES
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| 161 | jmp SHORT .BootMenu ; Show boot menu again
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| 162 | %endif ; MODULE_HOTKEYS
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| 163 |
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| 164 | %endif ; MODULE_BOOT_MENU
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| 165 |
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| 166 | ; No hotkeys and no boot menu means fixed "A then C" boot order
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| 167 | %ifndef MODULE_HOTKEYS OR MODULE_BOOT_MENU
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| 168 | xor dl, dl ; Try to boot from Floppy Drive A
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| 169 | call BootSector_TryToLoadFromDriveDL_AndBoot
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| 170 | mov dl, 80h ; Try to boot from Hard Drive C
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| 171 | call BootSector_TryToLoadFromDriveDL_AndBoot
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| 172 | %endif
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| 173 |
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| 174 | .RomBoot:
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| 175 | %ifdef MODULE_DRIVEXLATE
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| 176 | call DriveXlate_Reset ; Clean up any drive mappings before Rom Boot
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| 177 | %endif
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| 178 | clc
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| 179 | ;; fall through to Int19_JumpToBootSectorOrRomBoot
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| 180 |
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| 181 | ;--------------------------------------------------------------------
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| 182 | ; Int19_JumpToBootSectorOrRomBoot
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| 183 | ;
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| 184 | ; Switches back to the POST stack, clears the DS and ES registers,
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| 185 | ; and either jumps to the MBR (Master Boot Record) that was just read,
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| 186 | ; or calls the ROM's boot routine on interrupt 18.
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| 187 | ;
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| 188 | ; Parameters:
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| 189 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 190 | ; CF: Set for Boot Sector Boot
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| 191 | ; Clear for ROM Boot
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| 192 | ; ES:BX: (if CF set) Ptr to boot sector
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| 193 | ;
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| 194 | ; Returns:
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| 195 | ; Never returns
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| 196 | ;--------------------------------------------------------------------
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| 197 | Int19_JumpToBootSectorOrRomBoot:
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| 198 | mov cx, es ; Preserve MBR segment (can't push because of stack change)
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| 199 | mov ax, 0 ; NOTE: can't use XOR (LOAD_BDA_SEGMENT_TO) as it impacts CF
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| 200 | SWITCH_BACK_TO_POST_STACK
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| 201 |
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| 202 | ; clear segment registers before boot sector or rom call
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| 203 | mov ds, ax
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| 204 | mov es, ax
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| 205 | %ifdef USE_386
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| 206 | mov fs, ax
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| 207 | mov gs, ax
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| 208 | %endif
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| 209 | jnc SHORT .romboot
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| 210 |
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| 211 | ; jump to boot sector
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| 212 | push cx ; sgment address for MBR
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| 213 | push bx ; offset address for MBR
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| 214 | retf ; NOTE: DL is set to the drive number
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| 215 |
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| 216 | ; Boot by calling INT 18h (ROM Basic of ROM DOS)
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| 217 | .romboot:
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| 218 | int BIOS_BOOT_FAILURE_INTERRUPT_18h ; Never returns
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