Problem with error 01C9 - More than one Ethernet devices

Problem Description

Certain Thinkpads show a warning message at POST when a WLAN card with an Atheros chipset is present in the MiniPCI slot:

  WARNING
  01C9: More than one Ethernet devices are found. Remove one of them.
  Press <Esc> to continue.

At POST, the BIOS conducts a scan for ethernet devices. It does this by reading the "PCI Class Codes" of every connected device. If more than one ethernet device is found, it produces the 01C9 error message. Unlike other wireless cards, which identify themselves as "other" network adapters, Atheros identify themselves as "ethernet". This collides with the internal ethernet controller (also a PCI device) and produces the 01C9.

Affected Models

• T30
• R40
• A31p

Not affected are: T23, T40, X40 (please submit!!!)

Solution

The solution is to modify the Atheros EEPROM so that it correctly identifies itself as a "other network adapter" instead of "ethernet". No messing with vendor and device ID is necessary. Madwifi drivers will function without patching.

(code to do this in Linux will be posted)