INT 15 - SYSTEM - COPY EXTENDED MEMORY                                          
	AH = 87h
	CX = number of words to copy (max 8000h)
	ES:SI -> global descriptor table (see #00499)
Return: CF set on error
	CF clear if successful
	AH = status (see #00498)
Notes:	copy is done in protected mode with interrupts disabled by the default
	  BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. handler; many 386 memory managers perform the copy with
	  interrupts enabled
	on the PS/2IBM PS/2, any model 30-286 & "Tortuga" this function does not use the port 92h
	  for A20(Address line 20) The 80286 and higher CPUs allow addresses in real mode to extend slightly beyond the one megabyte mark, which causes an incompatibility with some older programs which expect such addresses to wrap back to the beginning of the address space.  For complete compatibility with the 8088, newer machines thus contain circuitry which permits the twenty-first address line (A20) to be disabled.  The CPU then effectively has only twenty address lines in real mode, just as the 8088 does, and addresses which would extend beyond the one megabyte mark wrap to the beginning of the address space.  See also High Memory Area, Real Mode. control, but instead uses the keyboard controller (8042).
	  Reportedly this may cause the system to crash when access to the
	  8042 is disabled in password server mode (see also PORTIBM PC Portable (uses same BIOS as XT) 0064h,#P0398)
	this function is incompatible with the OS/2 compatibility box
SeeAlso: AH=88h,AH=89h,INT 1F/AH=90h


(Table 00498)
Values for extended-memory copy status:
 00h	source copied into destination
 01h	parity error
 02h	interrupt error
 03h	address line 20 gating failed
 80h	invalid command (PCIBM PC,PCjr)
 86h	unsupported function (XTIBM PC XT,PS30IBM PS/2 Model 30 and below)


Format of global descriptor table:
Offset	Size	Description	(Table 00499)
 00h 16 BYTEs	zeros (used by BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly.)
 10h	WORD	source segment length in bytes (2*CX-1 or greater)
 12h  3 BYTEs	24-bit linear source address, low byte first
 15h	BYTE	source segment access rights (93h)
 16h	WORD	(286) zero
		(386+) extended access rights and high byte of source address
 18h	WORD	destination segment length in bytes (2*CX-1 or greater)
 1Ah  3 BYTEs	24-bit linear destination address, low byte first
 1Dh	BYTE	destination segment access rights (93h)
 1Eh	WORD	(286) zero
		(386+) extended access rights and high byte of destin. address
 20h 16 BYTEs	zeros (used by BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. to build CS and SS descriptors)