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bootasm.S: remove redundant A20 enable code

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chyyuu 2013-03-10 10:12:24 -04:00
parent 8a6deabc73
commit fe2e2c2f1d
2 changed files with 1 additions and 4 deletions
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2
code/lab1/Makefile
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@ -206,7 +206,7 @@ TERMINAL :=gnome-terminal
debug: $(UCOREIMG)
$(V)$(QEMU) -S -s -parallel stdio -hda $< -serial null &
$(V)sleep 2
$(V)$(TERMINAL) -e "gdb -q -x tools/gdbinit"
$(V)$(TERMINAL) -e "gdb -q -tui -x tools/gdbinit"
debug-nox: $(UCOREIMG)
$(V)$(QEMU) -S -s -serial mon:stdio -hda $< -nographic &

3
code/lab1/boot/bootasm.S
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@ -42,9 +42,6 @@ seta20.2:
movb $0xdf, %al # 0xdf -> port 0x60
outb %al, $0x60 # 0xdf = 11011111, means set P2's A20 bit(the 1 bit) to 1
movb $0xdf, %al # 0xdf -> port 0x60, do it again!
outb %al, $0x60 # 0xdf = 11011111, means set P2's A20 bit(the 1 bit) to 1
# Switch from real to protected mode, using a bootstrap GDT
# and segment translation that makes virtual addresses
# identical to physical addresses, so that the