PORTIBM PC Portable (uses same BIOS as XT) 0044-0047 - Microchannel - PROGRAMMABLE INTERVAL TIMER 2
SeeAlso: PORTIBM PC Portable (uses same BIOS as XT) 0040h,PORTIBM PC Portable (uses same BIOS as XT) 0048h

0044  RW  PIT  counter 3 (PS/2IBM PS/2, any model)
		used as fail-safe timer. generates an NMIsee Non-Maskable Interrupt on time out.
		for user generated NMIsee Non-Maskable Interrupt see at 0462.
0047  -W  PIT  control word register counter 3 (PS/2IBM PS/2, any model, EISA(Enhanced Industry-Standard Architecture) A 32-bit superset of the IBMInternational Busiuness Machines ATIBM PC AT's expansion bus (which is now known as the ISA or Industry-Standard Architecture bus).)
	bit 7-6 = 00  counter 3 select
		= 01  reserved
		= 10  reserved
		= 11  reserved
	bit 5-4 = 00  counter latch command counter 3
		= 01  read/write counter bits 0-7 only
		= 1x  reserved
	bit 3-0 = 00