INT 0A - IRQ2 - LPT2 (PC), VERTICAL RETRACE INTERRUPT (EGA,VGA)

Notes:	the TOPS and PCnet adapters use this interrupt request line by default
	DOS 3.2 revectors IRQ2 to a stack-switching routine; DOS 3.3+ does so
	  unless STACKS=0 has been set in CONFIG.SYS.  MS/PC-DOS 3.3+ use the
	  IBM Interrupt Sharing Protocol (see #02568) when hooking this IRQ
	on ATs and above, the physical data line for IRQ2 is labeled IRQ9 and
	  connects to the slave 8259.  The BIOS redirects the interrupt for
	  IRQ9 back here.
	under DESQview, only the INT 15h vector and BASIC segment address (the
	  word at 0000h:0510h) may be assumed to be valid for the handler's
	  process
	many VGA boards do not implement the vertical retrace interrupt,
	  including the IBM VGA Adapter where the traces are either cut or
	  removed
SeeAlso: INT 52"DESQview",INT 5A"DoubleDOS",INT 71,INT 7A"GO32"