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Kartik K. Agaram 2021-03-21 21:57:20 -07:00
parent 36dd179f49
commit 89db4ec100
1 changed files with 15 additions and 15 deletions
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30
boot.subx
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@ -64,12 +64,12 @@
}
# load remaining sectors from first two tracks of disk into addresses [0x7e00, 0x17800)
b4/copy-to-ah 2/imm8 # read sectors from disk
b4/copy-to-ah 2/imm8/read-drive
# dl comes conveniently initialized at boot time with the index of the device being booted
b5/copy-to-ch 0/imm8 # cylinder 0
b6/copy-to-dh 0/imm8 # head 0
b1/copy-to-cl 2/imm8 # second sector, 1-based
b0/copy-to-al 0x7d/imm8 # number of sectors to read = 2*63 - 1 = 125
b5/copy-to-ch 0/imm8/cylinder
b6/copy-to-dh 0/imm8/head
b1/copy-to-cl 2/imm8/sector # 1-based
b0/copy-to-al 0x7d/imm8/num-sectors # 2*63 - 1 = 125
# address to write sectors to = es:bx = 0x7e00, contiguous with boot segment
bb/copy-to-bx 0/imm16
8e/->seg 3/mod/direct 3/rm32/bx 0/r32/es
@ -78,12 +78,12 @@
0f 82/jump-if-carry disk_error/disp16
# load two more tracks of disk into addresses [0x17800, 0x27400)
b4/copy-to-ah 2/imm8 # read sectors from disk
b4/copy-to-ah 2/imm8/read-drive
# dl comes conveniently initialized at boot time with the index of the device being booted
b5/copy-to-ch 0/imm8 # cylinder
b6/copy-to-dh 2/imm8 # head
b1/copy-to-cl 1/imm8 # sector, 1-based
b0/copy-to-al 0x7e/imm8 # number of sectors to read = 2*63 = 126
b5/copy-to-ch 0/imm8/cylinder
b6/copy-to-dh 2/imm8/head
b1/copy-to-cl 1/imm8/sector # 1-based
b0/copy-to-al 0x7e/imm8/num-sectors # 2*63 = 126
# address to write sectors to = es:bx = 0x17800, contiguous with boot segment
bb/copy-to-bx 0x1780/imm16
8e/->seg 3/mod/direct 3/rm32/bx 0/r32/es
@ -92,12 +92,12 @@
0f 82/jump-if-carry disk_error/disp16
# load two more tracks of disk into addresses [0x27400, 0x37000)
b4/copy-to-ah 2/imm8 # read sectors from disk
b4/copy-to-ah 2/imm8/read-drive
# dl comes conveniently initialized at boot time with the index of the device being booted
b5/copy-to-ch 0/imm8 # cylinder
b6/copy-to-dh 4/imm8 # head
b1/copy-to-cl 1/imm8 # sector, 1-based
b0/copy-to-al 0x7e/imm8 # number of sectors to read = 2*63 = 126
b5/copy-to-ch 0/imm8/cylinder
b6/copy-to-dh 4/imm8/head
b1/copy-to-cl 1/imm8/sector # 1-based
b0/copy-to-al 0x7e/imm8/num-sectors # 2*63 = 126
# address to write sectors to = es:bx = 0x27400, contiguous with boot segment
bb/copy-to-bx 0x2740/imm16
8e/->seg 3/mod/direct 3/rm32/bx 0/r32/es