ACPI or Advanced Configuration and Power Interface. What is it and
how does it effect your computing experience?
ACPI - Advanced
Configuration and Power Interface - Genuine Intel?
- x86 Family 6 Model 15
table, or PDF was removed because it will not display on your device. Check back on a PC....
This is a mouthful. Basically it is the interface that controls the Advanced
Configuration of the processor, memory controller, and power (do I see a glimmer
of a smile? Yes, Overclocking!) on the motherboard
of your computer.
Now how does this relate to say a Core 2 Duo/Quad or i series processor and
Well if it is not configured properly your Operating System (OS) will not
display or USE all your processors!
What happened? I was crusin' along and wham! My system restarted. Ok, I'll
just wait and see why. It did not restart, it hung at the 'Starting Windows'
screen. I reset it and selected 'Safe Mode', it hung at the AVG driver in safe
Now this is bad, so I decided to do a little trouble shooting. I had
Dual Boot and have two versions of Windows 7 installed on other
partitions, 32 bit and 64 bit. So I tried to start one of those OS's but no
start, it hung.
Next I go to my trusty ERD cd and open up Ghost then install my last back up
(a week old). Boot - same problem, it hangs.
Now I decide to do the obvious, I run AVG, Trojan Remover, and Spy Sweeper.
Nothing. Now this has me scratching my head, why did the system restart then
I decide that I have all ready messed up the Dual Boot so I do a reinstall of XP. At
first the install came up with an script error on install. I am persistent and it does
the install. (This may be due to the BIOS failure that I found later on).
But I have a problem, there is only one processor showing in the
System Manage / Device Manager for the
ACPI. Strange, it should show four processors.
Perplexed I run Windows Update thinking that the driver was corrupt or to
old, after all this install cd had Service Pack 3 and that is a couple of years
Nope update doesn't do anything. Next I do a search on 'XP does not
recognize multiprocessors' Nothing of interest there, so I search on 'XP
does not recognize quad processor' same thing, how ever there was one page
from Microsoft TechNet that had a driver for Windows SP1, it would not install.
Next I go in to the BIOS and poked around, nothing worked.
Now I am thinking that something has happened to my motherboard, so I go to
ASUS and look at all the FAQ questions and answers. Nothing of interest there.
Next I look at the BIOS up dates for my motherboard, Volia' there are two
newer BIOS up dates and they have - ' Update for Newer CPU's!' I download
the update and run it.
Now I have all four processors but the Task Manager and Affinity II can't see
them. So why can't the two programs see the processors? The Device Manager does,
so why doesn't these two. I do a search in the registry for Intel, I find the
processors listed in a couple of places but the one that made me look for a long
time was the key -
HKEY_LOCAL_MACHINE\SYSTEM\ CurrentControlSet\Enum\ACPI\ GenuineIntel_ -_x86_Family_6_Model_15
Note the Advanced Configuration and Power Interface - if the
ACPI is not enabled in your BIOS, then this key
is not activated, and if it isn't activated the software installed on your
computer can not see all the processors in your computer.
So the installation of the new XP will not work because when I installed it
the ACPI was not active, no matter what I tried did not turn on the
ACPI in the
You will find more
processor Troubleshooting techniques in
Self Computer Repair Unleashed! 2nd Edition E-Book.
Self Computer Repair Unleashed! 2nd Edition.
Now I have a choice, reinstall XP again or reinstalled the Ghost image from
last week? I reinstall the Ghost image and now I have all the processors back.
Essentially I have recovered my system and did not loose any data, just a day of
work which in turn I learned something that will help you.
So what did I learn? That something wiped my BIOS. When I reset the BIOS I
did not notice that the ACPI option was disabled. Not paying attention to
the clues caused me to do a lot of work. Now I have to go reinstall my dual boot
setup to continue testing
On further investigation and testing I learned: BartPE, ERD Commander, or Windows 7 ERD do not have
Advanced Configuration and Power
drivers therefore they operate on one processor even if the processor is a Duo
or a Quad an i series processor.
Having suspected this when I finished the reinstall of Windows 7 I
used ERD Commander to make the new image of the partition. While waiting I
opened the Task Manager and it showed one processor plus the
Advanced Configuration and Power Interface driver was not loaded.
There maybe a way to slip stream the driver into the cd for the use of all
processors by ERD Commander. That will be an experiment for a future time.
(Note, slipstreaming the driver into the old PE did not work, the driver does
calls to the "kernal" that does not have the information for the APCI driver to
"hook" into so no APCI for older versions of PE - "Preinstall Environment"