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Irqs And Windows Xp


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#1 ikester7579

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Posted 18 September 2009 - 08:15 AM

When there is a hardware conflict in a computer, usually changing the IRQ fixes this.

IRQ = interrupt request.

How it works is that you have a bunch of hardware sending information to your CPU. How does your CPU know what information belongs to what hardware? And which should it process first or in some type of order?

Giving hardware a IRQ number is like giving a bunch of people who want to be served now, a number to be called upon. So the numbers make the hardware information have to line up to get processed in what ever order it needs to be.

Now what happens in IRQ conflicts is when two different hardwares have the "same" IRQ number, so they fight over who is going to get processed first. That can make the hardware seem to work slow, not work at all, or freeze you whole computer up. So changing the IRQ usually solves the problem. And this could be done in most operating sytems before XP.

Now what is different about XP that the IRQ changing is diabled? XP has what is called ACPI compliant system control. Which is an advaced way to run your computer, and is different from the other operating systems. What this thing does is that it controls the IRQs automatically. It assigns them even overriding the computer bios. And it constantly monitors the hardware and checks for conflicts. It leaves #9 IRQ open. If it detects any conflict, it re-routes the information by giving it the #9 IRQ number.

This was designed to constantly solve conflicts on the go without having to change numbers, or slot positions your hardware is plugged into.

But if you are having problems (and this can happen), then changing around hardware from slot to slot is about your only alternative. There is another alternative, but it's a 50/50 that it will work. And a 50/50 chance you computer will quit working (crash). So I won't mentioning it.

#2 ikester7579

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Posted 18 September 2009 - 07:00 PM

Here is a snap shot of the IRQ numbers that are assigned to the hardware in my computer.

Posted Image

You will notice that each hardware has a number (0-22). Some have the same number. It would be better if they did not, but Microsoft seems to think differently for one reason or another. Notice that the ACPI has number 9 IRQ. This is the free IRQ that I was speaking of in the first post. One that when conflict is detected, it re-routes it to use number 9.

So do you see how this makes the hardware line up and be different by number so that the computer knows what's what? Basically if the computer needs info from the hardware with say number 3 IRQ, that is what it will ask for. Or if the hardware want to send info to be processed by the CPU, but there is other information being processed, the IRQ number is made to wait in line to be processed. Instead of butting in and causing a slow up or lock up.

Now you might think IRQ waiting slows up your pc. The actual wait time can be measured in miliseconds, so most of the time you would not even notice a slow up. But without the IRQ system, the data stream traffic would be like a huge traffic jam. All the hardware trying to get processed at once would freeze up your pc. So basically IRQs give order to what could be chaos.

#3 ikester7579

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Posted 20 September 2009 - 02:02 AM

IRQ firestorming:

The ACPI system has a bug that affects "some" computers. It's where the IRQ requests are sent faster than the CPU can process it. This can make your computer act jerky. Videos play jerky, games play jerky (stop go skip forward etc...).

The fix for this is a registry tweak. Here are the steps:

1) Click start then click run.
2) In the box that shows up, type: regedit
3) In the next screen find: HKEY_LOCAL_MACHINE. Click on the plus sign (+) to extend.
4) Then find "system" and click the plus sign to extend.
5) Then find "current control set" and click plus to extend.
6) Then find "services" and click plus to extend.
7) Then find "ACPI" And click plus to extend.
8) Then find "parameters" And click on the folder, not the plus sign.

You will notice some stuff show up in the screen next to where you were doing stuff step by step. This screen is where sytem settings can be changed to the ACPI.

Attached File  IRQ_setting.jpg   5.99KB   43 downloads

Where is says attributes. You have to change this setting to 100. I know mine says 80, but I have experimenting.

Now I'm not giving out info on just how to change the setting because if you don't know. You should not do this. Also if atributes is not there, it will have to be added. It is best to get someone who knows just how to do this.

Now when you get someone to help you with this. You just open up the screen again through the run command. And registry edit will open right where you left off.

This is where one can read about this problem on the microsoft site.

http://support.microsoft.com/kb/834631




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