Problem with error 01C9 - More than one Ethernet devices
Problem Description
Certain ThinkPads show a warning message during 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 classify themselves as "ethernet". This collides with the internal ethernet controller (also a PCI device) and causes the 01C9 to appear.
Affected Models
Not affected are:
Solution
The solution is to modify the Atheros EEPROM so that the card correctly identifies itself as an "other" instead of an "ethernet" network adapter. No messing with vendor and device ID is necessary. Madwifi drivers will function properly.
(code to do this in Linux will be posted)