ACPI and A Multiprocessor System

DIY-Computer-Repair can help!

You will find more Troubleshooting techniques in the Self Computer Repair Unleashed! Manual.

Advanced Configuration and Power Interface (ACPI)

This is a mouthful. Basically it is the interface that controls the Advanced Configuration of the processor, memory controller, and power on the motherboard of your computer.

Now how does this relate to say a Core 2 Duo or Quad processor and motherboard?

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 mode.

Now this is bad, so I decided to do a little trouble shooting. I had installed 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 hang?

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. 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 old.

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 Taskmanager 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 ACPI - 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 registry.

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 Windows 7.

Hard Drives, Internal or External, All available at Newegg.com

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