Increasing IRQ priority reg tweak :)

[SoVieTiK]

The main components of your computer have an IRQ number assigned to them. With this tweak we can increase the priority given to any IRQ number, thereby improving the performance of that component. The most common component this tweak is used for is the System CMOS/real time clock, which improves performance across the board. First of all, decide which component you want to give a performance boost to. Next, you have to discover which IRQ that piece of hardware is using. To do this, simply go to Control Panel, then open the System panel (You can also press the shortcut of Windows+Break). Click the 'Hardware' tab, then on the 'Device Manager' button.



Now, right click on the component you want to discover the IRQ for and click 'Properties', then click on the 'Resources' tab.



You can plainly see which IRQ this device is using (if there is no IRQ number, select another device). Remember the number and close down all of the dialog boxes you have opened, then start up RegEdit. Navigate to HKEY_LOCAL_MACHINESystemCurrentControlSetControlPriorityControl in the registry. Now, we have to create a new DWORD value - called IRQ#Priority (where '#' is the IRQ number), then set the data to 1. For example, the IRQ of my System CMOS is 8, so I would create the key IRQ8Priority.



Now, after restarting, you should notice improved performance in the component you tweaked. I would strongly recommend the CMOS, as it improves performance around the board. Also note that you can have multiple IRQ prioritized, but it is fairly inefficient and can cause instability. To remove this tweak, simply delete the value you created.

 

[allan]

Actually, this well publicized tweak does little, if anything, in XP.

Rather than try my own clumsy explanation, let me quote someone far more technical than I, Rob Elder:

How the processor is interupted are determind by the IRQ number itself. The lowest number is the higer priority. Everything on the second chain has a higher priority than the first except the keyboard. This because the chains are hooked together on IRQ2---->IRQ9

The entries in the PriorityControl subkey in the registry determine the relative priority of foreground (active) applications to background (inactive) applications. This is a way to fine tune individual items instead of making a blanket choice in system properties.