1 Turbo Assembler Version 3.1 11/25/94 10:53:02 Page 1
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7 2 ;This boot sector is STUFFed to the gills to do a single
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8 3 ;stage boot of the MMURTL OS which is about 150K stored as
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9 4 ;a loadable image beginning at cluster 2 on the disk. The OS must
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10 5 ;be stored contiguously in each of the following logical sectors.
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11 6 ;The actual number of sectors is stored in the data param nOSSectors.
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13 8 0000 CSEG SEGMENT WORD 'Code' USE16
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14 9 ASSUME CS:CSEG, DS:CSEG, ES:Nothing
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18 13 0000 EB 48 JMP SHORT Bootup
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19 14 0002 90 NOP ;To use 3 bytes which aligned data
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21 16 ;OS Herald, Partition info begins here
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23 18 0003 4D 55 52 54 4C 31 2E+ Herald DB 'MURTL1.0'
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25 20 000B 0200 nBytesPerSect DW 0200h ;nBytes/Sector
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26 21 000D 01 nSectPerClstr DB 01h ;Sect/Cluster
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27 22 000E 0001 nRsvdSect DW 0001h ;Resvd sectors
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28 23 0010 02 nFATS DB 02 ;nFATs
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29 24 0011 00E0 nRootDirEnts DW 00E0h ;Root Dir entries max
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30 25 0013 0B40 nTotalSectors DW 0B40h ;nTotal Sectors (0 = <32Mb)
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31 26 0015 F0 bMedia DB 0F0h ;media desc. (worthless)
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32 27 0016 0009 nSectPerFAT DW 0009h ;nSect in FAT
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33 28 0018 0012 nSectPerTrack DW 0012h ;nSectors/track
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34 29 001A 0002 nHeads DW 0002h ;nHeads
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35 30 001C 00000000 nHidden DD 00000000h ;nHidden Sectors (first whole track on HD)
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36 31 0020 00000000 nTotalSect32 DD 00000000h ;nTotalSectors if > 32Mb
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38 33 0024 00 bBootDrive DB 00h ;Drive boot sector came from
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40 35 0025 00 ResvdByte DB 00h ;Used for temp storage of Sector to Read
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42 37 0026 29 ExtBootSig DB 29h ; Ext Boot Signature (always 29h)
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43 38 0027 0140 nOSSectors DW 0140h ; (140 sectors max) Was Volume ID number
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44 39 0029 0000 ResvdWord DW 0000h
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45 40 002B 52 49 43 48 20 20 20+ Volname DB 'RICH ' ;11 bytes for volume name
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47 42 0036 46 41 54 31 32 20 20+ FatType DB 'FAT12 ' ;8 bytes for FAT name (Type)
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50 45 003E 07FF IDTptr DW 7FFh ;LIMIT 256 IDT Slots
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51 46 0040 00000000 DD 0000h ;BASE (Linear)
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53 48 0044 17FF GDTptr DW 17FFh ;LIMIT 768 slots
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54 49 0046 00000800 DD 0800h ;BASE (Linear)
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56 51 ;Herald and partiton info ends here
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60 55 ;Boot blocks first instruction starts here after initial jump from beginning
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61 56 004A FA CLI ;Clear interrupts
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63 \fTurbo Assembler Version 3.1 11/25/94 10:53:02 Page 2
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68 58 ;Stick the stack at 98000h
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70 60 004B B8 9000 MOV AX,9000h
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71 61 004E 8E D0 MOV SS, AX
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72 62 0050 BC 8000 MOV SP, 8000h
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74 64 ;Move this boot sector UP to 90000h Linear.
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76 66 0053 B8 9000 MOV AX, 09000h
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77 67 0056 8E C0 MOV ES, AX
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78 68 0058 33 FF XOR DI, DI
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79 69 005A B8 07C0 MOV AX, 7C0h
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80 70 005D 8E D8 MOV DS, AX
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81 71 005F 33 F6 XOR SI, SI
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82 72 0061 B9 0200 MOV CX, 512
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83 73 0064 F3> A4 REP MOVSB
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85 75 ; Now we jump UP to where we moved it.
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87 77 0066 B8 9000 MOV AX, 09000h ;Segment
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89 79 006A B8 006F MOV AX, 6Fh ;Offset
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93 83 ; Now set DS equal to ES which is 9000h
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96 86 0071 8B 0E 0018r MOV CX, nSectPerTrack
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98 88 0075 33 C0 XOR AX, AX
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99 89 0077 8E D8 MOV DS, AX
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100 90 0079 BB 0078 MOV BX, 0078h ;Int 1E FDC Params!
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101 91 007C C5 37 LDS SI, DS:[BX]
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103 93 007E 88 4C 04 MOV BYTE PTR [SI+4], CL
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104 94 0081 C6 44 09 0F MOV BYTE PTR [SI+9], 0Fh
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112 102 0089 8A 16 0024r MOV DL, bBootDrive ;Required for Disk System Reset
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113 103 008D 33 C0 XOR AX, AX
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115 105 008F CD 13 INT 13h ;Reset Disk Controller (DL has drive num)
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116 106 0091 72 33 JC SHORT BadBoot ;Reset failed...
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120 110 ;The controller is reset, now let's read some stuff!!
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121 111 ;We are gonna skip checking to see if the first file
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122 112 ;really IS the OS. We need the space for other code.
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124 114 0094 BE 01EBr MOV SI, OFFSET MsgLoad
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125 \fTurbo Assembler Version 3.1 11/25/94 10:53:02 Page 3
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130 115 0097 E8 0038 CALL PutChars
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132 117 ;What we do now is calcualte our way to the third cluster
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133 118 ;on the disk and read in the total number of OS sectors in
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134 119 ;logical sector order. (3rd cluster is really the first allocated
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135 120 ; cluster because first 2 are unused).
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136 121 ;The layout of the Disk is:
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137 122 ; Boot Sector (at logical sector 0)
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138 123 ; Hidden Sectors (optional)
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139 124 ; FATS (1 or more)
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140 125 ; Additional Reserved sectors (optional)
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141 126 ; Root Directory (n Sectors long)
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143 128 009A 33 C0 XOR AX, AX
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144 129 009C A0 0010r MOV AL, nFATS
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145 130 009F F7 26 0016r MUL WORD PTR nSectPerFAT
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146 131 00A3 03 06 001Cr ADD AX, WORD PTR nHidden ;
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147 132 00A7 13 16 001Er ADC DX, WORD PTR nHidden+2
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148 133 00AB 03 06 000Er ADD AX, nRsvdSect
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149 134 00AF 8B C8 MOV CX, AX ;Save in CX
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151 136 ;CX now has a Word that contains the sector of the Root
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153 138 ;Calculate the size of the root directory and skip past it
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154 139 ;to the first allocated sectors (this is where the OS or
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155 140 ;stage one of the a two stage loader should be).
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157 142 00B1 B8 0020 MOV AX,0020h ;Size of Dir Entry
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158 143 00B4 F7 26 0011r MUL WORD PTR nRootDirEnts
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159 144 00B8 8B 1E 000Br MOV BX, nBytesPerSect
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160 145 00BC F7 F3 DIV BX
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161 146 00BE 03 C1 ADD AX, CX
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163 148 ;AX is at sector for cluster 0, but cluster 0 and 1 don't exist
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164 149 ;so we are really at cluster 2 like we want to be.
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166 151 00C0 8B 0E 0027r MOV CX, nOSSectors ;Number of OS sectors to read
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167 152 00C4 EB 1B JMP SHORT ContinueBoot
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169 154 ;Bad boot goes here and displays a message then
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170 155 ;waits for a key to reboot (or tries to) via int 19h
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173 158 00C6 BE 01DAr MOV SI, OFFSET MsgBadDisk
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174 159 00C9 E8 0006 CALL PutChars
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176 161 00CC 33 C0 XOR AX,AX
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177 162 00CE CD 16 INT 16h ;Wait for keystroke
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178 163 00D0 CD 19 INT 19h ;Sys Reboot
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182 167 00D3 0A C0 OR AL,AL
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183 168 00D5 74 09 JZ SHORT Done
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184 169 00D7 B4 0E MOV AH, 0Eh
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185 170 00D9 BB 0007 MOV BX,0007
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186 171 00DC CD 10 INT 10h
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187 \fTurbo Assembler Version 3.1 11/25/94 10:53:02 Page 4
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192 172 00DE EB F2 JMP SHORT PutChars
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196 176 00E1 ContinueBoot:
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197 177 00E1 BB 6000 MOV BX, 06000h ;This is segment where we load the OS.
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198 178 00E4 8E C3 MOV ES, BX
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200 180 00E6 NextSector:
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201 181 00E6 50 PUSH AX
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202 182 00E7 51 PUSH CX
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203 183 00E8 52 PUSH DX
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204 184 00E9 06 PUSH ES
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206 186 00EA 33 DB XOR BX, BX
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208 188 ; Read a logical sector to ES:BX
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209 189 ; AX has Logical Sector Number
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211 191 00EC 8B 36 0018r MOV SI, nSectPerTrack
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212 192 00F0 F7 F6 DIV SI ;Divide LogicalSect by nSectPerTrack
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213 193 00F2 FE C2 INC DL ;Sector numbering begins at 1 (not 0)
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214 194 00F4 88 16 0025r MOV ResvdByte, DL ;Sector to read
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215 195 00F8 33 D2 XOR DX, DX ;Logical Track left in AX
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216 196 00FA F7 36 001Ar DIV WORD PTR nHeads ;Leaves Head in DL, Cyl in AX
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217 197 00FE 8A 36 0024r MOV DH, bBootDrive
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218 198 0102 86 D6 XCHG DL, DH ;Head to DH, Drive to DL
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219 199 0104 8B C8 MOV CX, AX ;Cyl into CX
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220 200 0106 86 CD XCHG CL, CH ;Low 8 bits of Cyl to CH, Hi 2 bits to CL
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221 201 0108 C0 E1 06 SHL CL, 6 ; shifted to bits 6 and 7
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222 202 010B 0A 0E 0025r OR CL, BYTE PTR ResvdByte ;OR with Sector number
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223 203 010F B0 01 MOV AL, 1 ;Number of sectors
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224 204 0111 B4 02 MOV AH, 2 ;Read
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225 205 0113 CD 13 INT 13h ;Read that sucker!
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226 206 0115 72 AF JC SHORT BadBoot
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228 208 0117 BE 01FCr MOV SI, OFFSET MsgDot
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229 209 011A E8 FFB5 CALL PutChars
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236 216 0121 8C C3 MOV BX, ES
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237 217 0123 83 C3 20 ADD BX, 20h ;512 bytes for segment
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238 218 0126 8E C3 MOV ES, BX
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239 219 0128 40 INC AX ;Next Sector
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240 220 0129 E2 BB LOOP NextSector
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242 222 ;At this point we have the OS loaded in a contigous section
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243 223 ;from 60000 linear up to about 80000 linear.
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244 224 ;Now we disable interrupts, turn on the A20 line, move
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245 225 ;it down to address 0, set protected mode and JUMP!
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248 228 012C 33 C9 XOR CX,CX
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249 \fTurbo Assembler Version 3.1 11/25/94 10:53:02 Page 5
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255 230 012E E4 64 IN AL,64h
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256 231 0130 A8 02 TEST AL,02h
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257 232 0132 E0 FA LOOPNZ IBEmm0
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258 233 0134 B0 D1 MOV AL,0D1h
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259 234 0136 E6 64 OUT 64h,AL
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260 235 0138 33 C9 XOR CX,CX
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262 237 013A E4 64 IN AL,64h
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263 238 013C A8 02 TEST AL,02h
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264 239 013E E0 FA LOOPNZ IBEmm1
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265 240 0140 B0 DF MOV AL,0DFh
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266 241 0142 E6 60 OUT 60h,AL
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267 242 0144 33 C9 XOR CX,CX
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269 244 0146 E4 64 IN AL,64h
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270 245 0148 A8 02 TEST AL,02h
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271 246 014A E0 FA LOOPNZ IBEmm2
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273 248 ;A20 line should be ON Now
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274 249 ;So move the OS
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276 251 ; Set up our new DS to where we moved the data
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277 252 ; We must do this before each 32K load cause we use DS */
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279 254 014C BA 8000 MOV DX, 8000h
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281 256 ; Move 64K data chunk from linear 60000h to linear 0
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283 258 014F BB 6000 MOV BX, 06000h
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284 259 0152 8E DB MOV DS, BX
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285 260 0154 33 F6 XOR SI, SI
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286 261 0156 33 C0 XOR AX, AX
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287 262 0158 8E C0 MOV ES,AX
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288 263 015A 33 FF XOR DI,DI
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289 264 015C 8B CA MOV CX, DX
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291 266 015F F3> A5 REP MOVSW ;WORD move
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293 268 ; Move first 64K code chunk from linear 70000h to 10000h
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295 270 0161 BB 7000 MOV BX, 07000h
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296 271 0164 8E DB MOV DS, BX
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297 272 0166 33 F6 XOR SI, SI
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298 273 0168 B8 1000 MOV AX,1000h
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299 274 016B 8E C0 MOV ES,AX
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300 275 016D 33 FF XOR DI,DI
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301 276 016F 8B CA MOV CX, DX
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302 277 0171 F3> A5 REP MOVSW ;WORD move
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304 279 ; Move last code (32K) from linear 80000h to 18000h
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306 281 0173 8E DA MOV DS, DX ;DX is 8000h anyway
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307 282 0175 33 F6 XOR SI, SI
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308 283 0177 B8 2000 MOV AX,2000h
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309 284 017A 8E C0 MOV ES,AX
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310 285 017C 33 FF XOR DI,DI
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311 \fTurbo Assembler Version 3.1 11/25/94 10:53:02 Page 6
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316 286 017E 8B CA MOV CX, DX
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317 287 0180 F3> A4 REP MOVSB ;BYTE move
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319 289 0182 BB 9000 MOV BX, 9000h
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320 290 0185 8E DB MOV DS, BX
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322 292 0187 66| 33 D2 XOR EDX, EDX
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323 293 018A 8A 16 0024r MOV DL, bBootDrive ;OS can find bootdrive in DL on entry
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325 295 018E 0F 01 1E 003Er LIDT FWORD PTR IDTptr
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326 296 0193 0F 01 16 0044r LGDT FWORD PTR GDTptr
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328 298 0198 0F 20 C0 MOV EAX,CR0
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329 299 019B 0C 01 OR AL,1
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330 300 019D 0F 22 C0 MOV CR0,EAX
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331 301 01A0 EB 00 JMP $+2
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335 305 01A4 BB 0010 MOV BX, 10h
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336 306 01A7 8E DB MOV DS,BX
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337 307 01A9 8E C3 MOV ES,BX
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338 308 01AB 8E E3 MOV FS,BX
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339 309 01AD 8E EB MOV GS,BX
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340 310 01AF 8E D3 MOV SS,BX
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342 312 ;We define a far jump with 46 bit pointer manually
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346 316 01B3 EA DB 0EAh
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347 317 01B4 00010000 DD 10000h
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348 318 01B8 0008 DW 8h
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350 320 01BA 20 20 20 20 20 20 20+ MsgNone DB ' '
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351 321 20 20 20 20 20 20 20+
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352 322 20 20 20 20 20 20 20+
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353 323 20 20 20 20 20 20 20+
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355 325 01DA 0D 0A 42 61 64 20 42+ MsgBadDisk DB 0Dh, 0Ah, 'Bad Boot Disk!', 00h
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356 326 6F 6F 74 20 44 69 73+
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358 328 01EB 0D 0A 4C 6F 61 64 69+ MsgLoad DB 0Dh, 0Ah, 'Loading MMURTL', 00h
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359 329 6E 67 20 4D 4D 55 52+
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361 331 01FC 2E 00 MsgDot DB '.', 00h
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363 333 01FE AA5F BootSig DW 0AA5Fh
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367 \fTurbo Assembler Version 3.1 11/25/94 10:53:02 Page 7
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373 Symbol Name Type Value
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375 ??DATE Text "11/25/94"
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376 ??FILENAME Text "Bootblok"
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377 ??TIME Text "10:53:02"
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378 ??VERSION Number 030A
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381 @FILENAME Text BOOTBLOK
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383 BADBOOT Near CSEG:00C6
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384 BBOOTDRIVE Byte CSEG:0024
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385 BMEDIA Byte CSEG:0015
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386 BOOTSIG Word CSEG:01FE
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387 BOOTUP Near CSEG:004A
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388 CONTINUEBOOT Near CSEG:00E1
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389 DONE Near CSEG:00E0
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390 EXTBOOTSIG Byte CSEG:0026
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391 FATTYPE Byte CSEG:0036
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392 GDTPTR Word CSEG:0044
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393 HERALD Byte CSEG:0003
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394 IBEMM0 Near CSEG:012E
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395 IBEMM1 Near CSEG:013A
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396 IBEMM2 Near CSEG:0146
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397 IDTPTR Word CSEG:003E
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398 MSGBADDISK Byte CSEG:01DA
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399 MSGDOT Byte CSEG:01FC
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400 MSGLOAD Byte CSEG:01EB
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401 MSGNONE Byte CSEG:01BA
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402 NBYTESPERSECT Word CSEG:000B
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403 NEXTSECTOR Near CSEG:00E6
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404 NFATS Byte CSEG:0010
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405 NHEADS Word CSEG:001A
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406 NHIDDEN Dword CSEG:001C
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407 NOSSECTORS Word CSEG:0027
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408 NROOTDIRENTS Word CSEG:0011
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409 NRSVDSECT Word CSEG:000E
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410 NSECTPERCLSTR Byte CSEG:000D
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411 NSECTPERFAT Word CSEG:0016
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412 NSECTPERTRACK Word CSEG:0018
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413 NTOTALSECT32 Dword CSEG:0020
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414 NTOTALSECTORS Word CSEG:0013
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415 PUTCHARS Near CSEG:00D2
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416 RESVDBYTE Byte CSEG:0025
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417 RESVDWORD Word CSEG:0029
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418 VOLNAME Byte CSEG:002B
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420 Groups & Segments Bit Size Align Combine Class
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422 CSEG 16 0200 Word none CODE
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projects / mmurtl / blob