Answer to: To upgrade to Sierra I need to upgrade WIFI card.I am running Sierra successfully on a 2007 24" iMac (7,1) after upgrading the CPU from a T7700 to a T9500 (Penryn) and applying dosdude's Sierra patch. (If your 2008 already has a Penryn chip you don't need to do that part!) Also having the Broadcom wifi incompatibility problem, but I don't really need that on this machine. The unsupported wifi does not prevent Sierra from running. The system just doesn't see any wifi hardware. If I do someday want to replace the wifi hardware, does anyone know what model would work and has the right form factor for this machine?