Signs of non-idleness (MS POWER):
- int 10.func > 3
- int 13
- int 14.func != 3
- int 17.func != 2
- int 6c.??? (?)
- int 16.0/1/10/11
- IRQs (already handled by BIOS)
Signs of idleness:
- int 2a.84 network keyboard waiting (MS POWER)
- int 28 dos idle (addition Eric) (any int 21 but 0..c ok in handler)
Signs of non-idleness (Eric):
- int 21.4b end idle (not needed probably)
- int 2f.ae end idle

What to do if idle (MS auto-selects both/one only):
- sti hlt
- int 15.5305 set cpu idle
What to do if non-idle:
- int 15.5306 set cpu busy (probably only for "disable APM" usage!)

Flush caches before triggering:
- int 15.5307.bx=1.cx=3 turn off system (needs APM 1.1+)
- int 15.5307.bx=1.cx=2 suspend system
- int 15.5307.bx=1.cx=1 system stand-by
- cold reboot (ffff:0000 or out 64,fe)
- warm reboot (set 40:72 to 1234, ffff:0000)
- hot reboot (int 19)

Init sequence:
- int 15.5300.bx=0 install check -> version ah.al
- int 15.5301.bx=0 real mode connect: NC is okay, AH=2 is already conn.
- int 15.530f.bx=1.cx=1 engage power management (like func 8, but
  cooperative: BIOS APM keeps working in parallel)
- int 15.5308.bx=1(for apm 1.0, use -1).cx=0/1 disable/enable APM
- int 15.530e.bx=00 enable APM version CX, e.g. like AX of func 0
- int 15.530d.bx=1.cx=1 enable CPU management

Other vendor specific things:
(int 15.5380.bh=d.cl=divider(1/2/4/8).bl=mode??? set speed APM SL Enh.)
(int 15.5380.bh=c get cpu speed divider CL, mode BL APM SL Enhanced)
(int 15.da01.cl=... AMI PCI BIOS speed get/set: 0/1 set lo/hi, 2 get)
(int 15.da92 get cpu type BL.AH.AL / fsb speed CX in bcd)
(int 16.f0xx compaq 386 set cpu speed: 0..2 - get is int 16.f1 -> al)
((int 1f.fb.bl=... get/set Chips and Tech SuperState BIOS CPU speed))

Battery status reading:
int 15.530a.bx=1 get AC/batt status BH (0 off 1 online 2 ups -1 unk),
  BL=battery status (0 hi, 1 lo, 2 crit, 3 charging -1 unknown),
  CH=battery flag (...), CL=battery percentage (binary, -1=unknown)
  DX=remaining (msb=min/not-sec, other bits=value, -1=unknown)
  CH/DX apm 1.1 only.

Cache flushing (from APMlib by Aitor Santamaria-Merino):
CDBlitz: int 2f.1500.ch=90.bx=1234 -> if returned cx=1234,
  int 2f.1500.ch=96.bx=1234 - status: carry
PC-Cache: int 16.ffa5.cx=1111 -> if returned cx=0, int 16.ffa5.cx=-1
Quick Cache: int 13.27.bx=0 -> if returned ax=0, bx!=0, int 13.0021 (?)
  - status: ax != 0 if error
Super PC-Kwik (PC-Tools, QCache): int 21.2b.cx=4358 -> if returns al=0,
  int 13.00a1 (?).si=4358 - status: carry
MS SMARTDRV EXE: int 2f.4a10.bx=0.cx=ebab -> if returned ax=babe,
  int 2f.4a10.bx=1 - NOTE: 2f.4a01.bx=1 was wrong! Corrected 9/2009
MS SMARTDRV SYS: open/reset "smartaar" file. if it works,
  int 21.4403.bx=filehandle.cx=0.ds:dx=buffer with byte 2 in it
  - status carry
generic: int 21.0d, then int 13.0000.dl=80 - status carry

POWER.EXE API:
int 2f.5400 install check - return version ah.al bx=504d
int 2f.5401.bh=0/1 get/set status BL: 2lsb are 0 off 2 std 3 adv - re-
  turn status ax: 0 ok 2 already connected 3 not connected 87 inv. arg.
int 2f.5402.bh=0/xx get to BL / set to BH idle detection strategy
int 2f.5403.bx=0/xxxx get to BX / set setting: 1..5=min 6=reg 7..8=max
int 2f.5481.bx=0/1 get idleness/APM stats.cx=buffer len.ds:si=buffer
  contents idleness: dd cpu_on_time (in ticks), dd cpu_idle_time (...),
    dd idle call count, dd int 2f i. c. count, dd int 28 i. c. count
    dd int 16 idle call count, dd int 2a idle call count
  contents APM: dd count of resumes since last apm enable
int 2f.5482.bx=0/xxxx get to BX / set to xxxx APM polling frequency
int 2f.5481.bx=-1 reset idleness/APM statistics
  (FDAPM 2/2005 and newer, NOT part of the official POWER.EXE API!)

For the archives - license disclaimer of versions before Nov 26 2003:
; A tool for APM power management in FreeDOS.
; Copyright Eric Auer 2003. Please do not spread - just send
; me (NASM) CODE to complete the project! When done, you will
; be credited and the project will be released under GPL 2.
; Please read apmnotes.txt for an outline of the workings.

ACPI information:
Read acpitool.asm source or check the ACPI specs at www.acpi.info ;-).

