1 | ; Project name : XTIDE Universal BIOS
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2 | ; Description : Functions for accessings RAMVARS.
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3 |
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4 | ; Section containing code
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5 | SECTION .text
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6 |
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7 | ;--------------------------------------------------------------------
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8 | ; Initializes RAMVARS.
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9 | ; Drive detection can be started after this function returns.
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10 | ;
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11 | ; RamVars_Initialize
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12 | ; Parameters:
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13 | ; Nothing
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14 | ; Returns:
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15 | ; Nothing
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16 | ; Corrupts registers:
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17 | ; AX, CX, DI, DS
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18 | ;--------------------------------------------------------------------
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19 | ALIGN JUMP_ALIGN
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20 | RamVars_Initialize:
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21 | push es
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22 | call .StealMemoryForRAMVARS ; Get RAMVARS segment to DS even if no stealing
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23 | call .ClearRamvarsFromDS
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24 | pop es
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25 | jmp DriveXlate_Reset
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26 |
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27 | ;--------------------------------------------------------------------
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28 | ; .StealMemoryForRAMVARS
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29 | ; Parameters:
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30 | ; Nothing
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31 | ; Returns:
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32 | ; DS: RAMVARS segment
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33 | ; Corrupts registers:
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34 | ; AX
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35 | ;--------------------------------------------------------------------
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36 | ALIGN JUMP_ALIGN
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37 | .StealMemoryForRAMVARS:
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38 | test BYTE [cs:ROMVARS.wFlags], FLG_ROMVARS_FULLMODE
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39 | jz SHORT RamVars_GetSegmentToDS
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40 |
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41 | LOAD_BDA_SEGMENT_TO ds, ax ; Zero AX
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42 | mov al, [cs:ROMVARS.bStealSize]
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43 | sub [BDA.wBaseMem], ax
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44 | mov ax, [BDA.wBaseMem]
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45 | eSHL_IM ax, 6 ; Segment to first stolen kB (*=40h)
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46 | mov ds, ax
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47 | ret
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48 |
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49 | ;--------------------------------------------------------------------
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50 | ; .ClearRamvarsFromDS
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51 | ; Parameters:
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52 | ; DS: RAMVARS segment
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53 | ; Returns:
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54 | ; Nothing
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55 | ; Corrupts registers:
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56 | ; AX, CX, DI, ES
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57 | ;--------------------------------------------------------------------
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58 | ALIGN JUMP_ALIGN
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59 | .ClearRamvarsFromDS:
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60 | call FindDPT_PointToFirstDPT ; Get RAMVARS/FULLRAMVARS size to DI
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61 | mov cx, di ; Copy byte count to CX
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62 | push ds
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63 | pop es
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64 | xor di, di ; ES:DI now points to RAMVARS/FULLRAMVARS
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65 | xor ax, ax ; Store zeroes
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66 | rep stosb
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67 | mov WORD [FULLRAMVARS.wSign], W_SIGN_FULLRAMVARS
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68 | ret
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69 |
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70 |
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71 | ;--------------------------------------------------------------------
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72 | ; Returns segment to RAMVARS.
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73 | ; RAMVARS might be located at the top of interrupt vectors (0030:0000h)
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74 | ; or at the top of system base RAM.
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75 | ;
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76 | ; RamVars_GetSegmentToDS
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77 | ; Parameters:
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78 | ; Nothing
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79 | ; Returns:
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80 | ; DS: RAMVARS segment
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81 | ; Corrupts registers:
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82 | ; DI
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83 | ;--------------------------------------------------------------------
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84 | ALIGN JUMP_ALIGN
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85 | RamVars_GetSegmentToDS:
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86 | test BYTE [cs:ROMVARS.wFlags], FLG_ROMVARS_FULLMODE
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87 | jnz SHORT .GetStolenSegmentToDS
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88 | mov di, SEGMENT_RAMVARS_TOP_OF_INTERRUPT_VECTORS
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89 | mov ds, di
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90 | ret
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91 |
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92 | ALIGN JUMP_ALIGN
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93 | .GetStolenSegmentToDS:
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94 | LOAD_BDA_SEGMENT_TO ds, di
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95 | mov di, [BDA.wBaseMem] ; Load available base memory size in kB
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96 | eSHL_IM di, 6 ; Segment to first stolen kB (*=40h)
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97 | ALIGN JUMP_ALIGN
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98 | .LoopStolenKBs:
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99 | mov ds, di ; EBDA segment to DS
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100 | add di, BYTE 64 ; DI to next stolen kB
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101 | cmp WORD [FULLRAMVARS.wSign], W_SIGN_FULLRAMVARS
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102 | jne SHORT .LoopStolenKBs ; Loop until sign found (always found eventually)
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103 | ret
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104 |
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105 |
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106 | ;--------------------------------------------------------------------
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107 | ; Checks if INT 13h function is handled by this BIOS.
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108 | ;
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109 | ; RamVars_IsFunctionHandledByThisBIOS
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110 | ; Parameters:
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111 | ; AH: INT 13h function number
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112 | ; DL: Drive number
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113 | ; DS: RAMVARS segment
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114 | ; Returns:
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115 | ; CF: Set if function is handled by this BIOS
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116 | ; Cleared if function belongs to some other BIOS
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117 | ; Corrupts registers:
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118 | ; DI
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119 | ;--------------------------------------------------------------------
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120 | ALIGN JUMP_ALIGN
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121 | RamVars_IsFunctionHandledByThisBIOS:
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122 | test ah, ah ; Reset for all floppy and hard disk drives?
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123 | jz SHORT .FunctionIsHandledByOurBIOS
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124 | cmp ah, 08h ; Read Disk Drive Parameters?
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125 | jne SHORT RamVars_IsDriveHandledByThisBIOS
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126 | test dl, 80h ; We dot not handle floppy drives
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127 | jz SHORT .FunctionIsNotHandledByOurBIOS
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128 | ALIGN JUMP_ALIGN
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129 | .FunctionIsHandledByOurBIOS:
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130 | stc
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131 | .FunctionIsNotHandledByOurBIOS:
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132 | ret
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133 |
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134 | ;--------------------------------------------------------------------
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135 | ; Checks if drive is handled by this BIOS.
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136 | ;
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137 | ; RamVars_IsDriveHandledByThisBIOS
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138 | ; Parameters:
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139 | ; DL: Drive number
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140 | ; DS: RAMVARS segment
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141 | ; Returns:
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142 | ; CF: Set if drive is handled by this BIOS
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143 | ; Cleared if drive belongs to some other BIOS
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144 | ; Corrupts registers:
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145 | ; DI
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146 | ;--------------------------------------------------------------------
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147 | ALIGN JUMP_ALIGN
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148 | RamVars_IsDriveHandledByThisBIOS:
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149 | xchg di, ax ; Backup AX
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150 | mov ax, [RAMVARS.wDrvCntAndFirst] ; Drive count to AL, First number to AH
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151 | add al, ah ; One past last drive to AL
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152 | cmp dl, al ; Above last supported?
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153 | jae SHORT .DriveNotHandledByThisBIOS
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154 | cmp dl, ah ; Below first supported?
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155 | jb SHORT .DriveNotHandledByThisBIOS
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156 | xchg ax, di
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157 | stc
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158 | ret
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159 | ALIGN JUMP_ALIGN
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160 | .DriveNotHandledByThisBIOS:
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161 | xchg ax, di
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162 | clc
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163 | ret
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164 |
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165 |
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166 | ;--------------------------------------------------------------------
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167 | ; Increments hard disk count to RAMVARS.
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168 | ;
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169 | ; RamVars_IncrementHardDiskCount
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170 | ; Parameters:
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171 | ; DL: Drive number for new drive
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172 | ; DS: RAMVARS segment
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173 | ; Returns:
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174 | ; Nothing
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175 | ; Corrupts registers:
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176 | ; Nothing
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177 | ;--------------------------------------------------------------------
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178 | ALIGN JUMP_ALIGN
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179 | RamVars_IncrementHardDiskCount:
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180 | inc BYTE [RAMVARS.bDrvCnt] ; Increment drive count to RAMVARS
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181 | cmp BYTE [RAMVARS.bFirstDrv], 0 ; First drive set?
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182 | ja SHORT .Return ; If so, return
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183 | mov [RAMVARS.bFirstDrv], dl ; Store first drive number
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184 | ALIGN JUMP_ALIGN
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185 | .Return:
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186 | ret
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187 |
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188 |
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189 | ;--------------------------------------------------------------------
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190 | ; RamVars_GetHardDiskCountFromBDAtoCX
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191 | ; Parameters:
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192 | ; DS: RAMVARS segment
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193 | ; Returns:
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194 | ; CX: Total hard disk count
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195 | ; Corrupts registers:
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196 | ; Nothing
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197 | ;--------------------------------------------------------------------
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198 | ALIGN JUMP_ALIGN
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199 | RamVars_GetHardDiskCountFromBDAtoCX:
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200 | push es
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201 | push dx
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202 |
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203 | LOAD_BDA_SEGMENT_TO es, cx ; Zero CX
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204 | call RamVars_GetCountOfKnownDrivesToDL
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205 | MAX_U dl, [es:BDA.bHDCount]
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206 | mov cl, dl
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207 |
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208 | pop dx
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209 | pop es
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210 | ret
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211 |
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212 | ;--------------------------------------------------------------------
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213 | ; RamVars_GetCountOfKnownDrivesToDL
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214 | ; Parameters:
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215 | ; DS: RAMVARS segment
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216 | ; Returns:
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217 | ; DL: Total hard disk count
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218 | ; Corrupts registers:
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219 | ; Nothing
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220 | ;--------------------------------------------------------------------
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221 | ALIGN JUMP_ALIGN
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222 | RamVars_GetCountOfKnownDrivesToDL:
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223 | mov dl, [RAMVARS.bFirstDrv] ; Number for our first drive
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224 | add dl, [RAMVARS.bDrvCnt] ; Our drives
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225 | and dl, 7Fh ; Clear HD bit for drive count
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226 | ret
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227 |
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228 |
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229 | ;--------------------------------------------------------------------
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230 | ; RamVars_GetIdeControllerCountToCX
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231 | ; Parameters:
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232 | ; Nothing
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233 | ; Returns:
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234 | ; CX: Number of IDE controllers to handle
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235 | ; Corrupts registers:
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236 | ; Nothing
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237 | ;--------------------------------------------------------------------
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238 | ALIGN JUMP_ALIGN
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239 | RamVars_GetIdeControllerCountToCX:
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240 | mov cx, 1 ; Assume lite mode (one controller)
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241 | test BYTE [cs:ROMVARS.wFlags], FLG_ROMVARS_FULLMODE
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242 | jz SHORT .Return
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243 | mov cl, [cs:ROMVARS.bIdeCnt]
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244 | ALIGN JUMP_ALIGN, ret
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245 | .Return:
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246 | ret
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