standard A20 
Author Message
 standard A20

  Does we have a standard way to enable A20 ? If no , why it said we can do
a faster way on PS/2 comaptible ?
Do we have to consider on the keyboard chipset?
thanks a lot!!!

Q: How do I enable and disable A20 gate?
A: Common way to enable A20 on all AT-compatibles is:
 mov al, 0D1h
 out 64h, al
 mov al, 0DFh
 out 60h, al

To disable A20 on AT-compatibles:
 mov al, 0D1h
 out 64h, al
 mov al, 0DDh
 out 60h, al

There is a faster way to do it on PS/2 comaptibles:
; Enable A20.
 in al, 92h
 or al, 2
 out 92h, al

;Disable A20.
 in al, 92h
 and al, NOT 2
 out 92h, al

Sat, 23 Nov 2002 03:00:00 GMT  
 [ 1 post ] 

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