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PC Reboots when a Lucent Orinoco WLAN Card is Inserted

This problem effects both Laptop and Desktop PC's (with PCI or ISA PCMCIA adapters) running Windows 95,98,98SE & Me (probably Windows 2000/XP as well, but we haven't seen this yet!). It also will effect other similar re-badged Lucent Wireless LAN cards from Cabletron, Enterasys, Dell and others. It might also effect WLAN cards made by other manufacturers if they indicate to the operating system that their IRQ may be shared.
It is not a problem with the P-series so other PCMCIA cards will work perfectly well in the adapter, in fact this problem can be reproduced on a laptop.

Symptoms:

When a Lucent WaveLAN (Orinoco) card is inserted into the PCMCIA slot, or the Lucent card is already inserted and another PCMCIA card is inserted into the adjacent PCMCIA slot, the PC immediately reboots. When you boot the PC with the Lucent WaveLAN(Orinoco) card and another PCMCIA card in the adjacent PCMCIA slot, the PC reboots, then reboots, then reboots..... for ever!

Reason for this problem:

The Lucent WaveLAN Wireless LAN drivers are not able to share an interrupt with a PCI device in the Laptop/Desktop PC. When available IRQ resources are low and a second PCMCIA card requiring an IRQ is inserted into an adjacent PCMCIA slot, Windows will re-balance the resources in the PC to free up an IRQ for the new device. 
The Lucent WLAN card reports that it is able to share it's IRQ, so Windows allocates it an IRQ that is assigned to a PCI device. The trouble is, a PCMCIA card is technically an "ISA" device when speaking in terms of it's IRQ's, so now two very different devices are sharing an IRQ that can only be steered correctly on the motherboard to one of them. So Windows cannot even hope to be able to configure the IRQ properly for both devices at the same time and fails to do it. Then an interrupt occurs from one of the devices which then just runs away un-handled causing a stack overflow and eventually the reboot. 

Solution:

NB: Please make sure you have backed up the registry and your important files before you do this. Elan cannot be held responsible for any problems that may occur!

  1. From the start menu "Run..." command, type "regedit" in the box and click OK
  2. Navigate to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Net\000x were x is a number (0,1,2 etc). There may be several network interfaces installed, and each PC is likely to be different, so you need to look in each one until you find the right key.
  3. Check that the "DriverDesc" entry is the expected one of the card (e.g. on my PC it says "WaveLAN/IEEE PC Card (5volt)", yours may have "Orinoco" or something like that). If it does not match the expected or similar text then try one of the other keys under HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Net until you find one that matches.
  4. Click "Registry" "Export Registry File" and save the selected key to a file so that you can restore it later (just in case you make a mistake or want to restore the original settings).
  5. Find the binary entry that's called "EnableIRQSharing" and delete it.
  6. Close the registry editor and re-boot the PC.