Increase Broadband Connection Speed in Windows XP

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:

1. Open the System Information tool by running MSINFO32.EXE from the Run command.
   
2. Expand System Summary > Hardware Resources > IRQs.
   
3. 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:

1. Open the Device Manager tool by running DEVMGMT.MSC from the Run command (or by right-clicking My Computer > Hardware tab > Device Manager button).
   
2. Scroll down to Universal Serial Bus controllers and expand it.
   
3. 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.
   

4. In the Power tab, look for your USB ADSL modem.
   
5. In the Resources tab look for the assigned IRQ (in this case - IRQ21).
   

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6. 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:

1. Run SYSEDIT.EXE from the Run command.
   
2. Expand the system.ini file window.
   
3. Scroll down almost to the end of the file till you find a line called [386enh].
   
4. 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!!!

5. Click on the File menu, then choose Save.
   
6. Close SYSEDIT and reboot your computer.
   

Done. Speed improvement will be noticed after the computer reboots.
QoS Packet Scheduler is a method of network bandwidth management that can monitor the importance of data packets and depending upon the priority of the packet, give it higher or lower priority or bandwidth levels. It's not very useful unless you're using apps which are QoS-aware or running a server, so you can gain some network overhead back by turning it off.
Note: This following tip will not work on XP Home Edition.

1. Make sure you're logged on as actually "Administrator". Do not log on with any account that just has administrator privileges.
2. Start > Run > type gpedit.msc (not available in home version).
3. Expand the Local Computer Policy branch.
4. Expand the Administrative Templates branch.
5. Expand the Network branch.
6. Highlight the "QoS Packet Scheduler" in left window.
7. In right window double click the "limit reservable bandwidth" setting.
8. On setting tab check the ENABLED item.
9. Where it says "Bandwidth limit %" change it to read 0 (ZERO).
10. Close gpedit.msc.

Effect is immediate on some systems, some need to re-boot.