I will be using the PIT 2, timer 0 for periodic realtime services. The IBM
PC dogma of using the NMI and related timer for a RAM watchdog timer is
inappropriate for a personal computer, and your meta-megabuck
e-frastructure server running Ha3sm should be safe-failover four levels
deep anyway.

This primary initial use of the ticker, the NMI clock, will be feeding
audio to the PC speaker. If I can get 1.19 mhz it might not suck as bad as
CDs. The problem is the ceremonies involved in flipping the voltage, i.e.
the "bit", fed to the speaker.

Squeal Mode will want a rmode NMI reflex.




















PORT 0070-007F - CMOS RAM/RTC (REAL TIME CLOCK)
Note:   the real-time clock may be either a discrete MC146814, MC146818, or
          an emulation thereof built into the motherboard chipset
SeeAlso: PORT 00A0h"XT"

0070  -W  CMOS RAM index register port (ISA, EISA)
                 bit 7  = 1  NMI disabled from reaching CPU
                        = 0  NMI enabled
                 bit 6-0     CMOS RAM index
                        (64 bytes in early systems, now usually 128 bytes)
        Note:   any write to PORT 0070h should be followed by an action to
                  PORT 0071h or the RTC wil be left in an unknown state.


0044  RW  PIT  counter 3 (PS/2)
                used as fail-safe timer. generates an NMI on time out.
                for user generated NMI see at 0462.
0047  -W  PIT  control word register counter 3 (PS/2, EISA)
        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
----------P0048004B--------------------------
PORT 0048-004B - EISA - PROGRAMMABLE INTERVAL TIMER 2
Note:   this second timer is also supported by many Intel chipsets
SeeAlso: PORT 0040h,PORT 0044h

0048  RW  EISA PIT2 counter 3 (Watchdog Timer)
0049  ??  EISA 8254 timer 2, not used (counter 4)
004A  RW  EISA PIT2 counter 5 (CPU speed control)
004B  -W  EISA PIT2 control word

