Increase Broadband Connection Speed in Windows XP/2003
by Daniel Petri - January 8, 2009

This tip is designed for increased BROADBAND speed in Windows XP while using standard Network Interface cards (NIC) that are connected to ADSL modems, or when using any directly-connected USB ADSL modem.

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To speed up the Internet connection speed we need to configure a special buffer in the computer's memory in order to enable it to better deal with interrupts made from the NIC or the USB modem.

This tip is only recommended if you have 256MB RAM or higher.
Step #1 - Identify the IRQ used by the NIC/USB modem

Follow these steps:

Open the System Information tool by running MSINFO32.EXE from the Run command.

Expand System Summary > Hardware Resources > IRQs.

Look for the listing made for your NIC (in my case - a Intel(R) PRO/100+ Management Adapter). Note the IRQ next to the specified line (in my case - IRQ21).


In case of USB modems you will first need to find the right USB device used by your modem. Follow these steps:

Open the Device Manager tool by running DEVMGMT.MSC from the Run command (or by right-clicking My Computer > Hardware tab > Device Manager button).

Scroll down to Universal Serial Bus controllers and expand it.

Right-click the USB Root Hub and select Properties. Note that you might need to do so for all listed USB Root hubs (if there are more than one) in order to find the right one.


In the Power tab, look for your USB ADSL modem.

In the Resources tab look for the assigned IRQ (in this case - IRQ21).



This is the IRQ we're looking for.

Lamer note: IRQs and modem names might vary...
Step #2 - Modify the system.ini file

Follow these steps:

Run SYSEDIT.EXE from the Run command.

Expand the system.ini file window.

Scroll down almost to the end of the file till you find a line called [386enh].

Press Enter to make one blank line, and in that line type

IrqX=4096

where X is the designated IRQ number we found in step #1, in my case it's IRQ21.


Note: This line IS CASE SENSITIVE!!!

Click on the File menu, then choose Save.

Close SYSEDIT and reboot your computer.

Done. Speed improvement will be noticed after the computer reboots.

Update: The most speed improvement is visible with USB A/DSL modems, however there are reports that this tweak also does good for regular NICs. In any case, it won't harm your system, so why not try it yourself and let me know what you find.