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A20GATE.ASM - attempts to enable the #A20 line for
              access to the HMA from realmode code

Created by  : Hayden McKay - build (j)54177

returns     : * [BX] [CX] will be destroyed
              * [AL] is non-zero on success

Thanks      : Ralf Brown's port list reference - ports.a
              and other various recorces on the internet!
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General Notes:
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        * Software interrupts will be restored after module execution
        * Check status with TEST AL, -1 / JNZ SUCCESS
	* Module should be paragraph aligned.

	If the #A20 line could not be asserted jumping to 0ffffh:010h
        (HMA) causes a system re-boot.
FAQ:
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        * Many chipsets badly handle 'FAST #A20 GATE' useing PORT-92h
        * Chipsets with 'FAST #A20 GATE' hook KB-8255 PORT-64h
        * Some BIOS's badly handle INT15H 2400h -> 2403h

