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Collection of Tools & Utilities
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ubppmpqs.zip
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ppmp1.asm
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Assembly Source File
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1993-03-14
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485b
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41 lines
;ppmp1.asm
;check if A20 line is enable.
.286p
code segment
assume cs:code,ds:code
include ubp.mac
org 100h
start:
xor ax,ax
mov ds,ax
dec ax
mov es,ax
xor si,si
mov di,0010h
mov cx,0200h
repe cmpsw
je cannotuse
smsw ax
test al,1
jnz virtual86
xor ax,ax
outret:
mov bx,AR0
mov word ptr cs:[bx],ax
mov ax,ss
mov ds,ax
mov es,ax
retf
cannotuse:
mov ax,1
jmp outret
virtual86:
mov ax,2
jmp outret
code ends
end start