I recently acquired a 2009 model Mac Pro Quad-Core Intel Xeon and needed to install a wireless card. Since Airport cards are not a user-installed option, Apple doesn’t publish documentation. Fortunately, though, detailed instructions can be found on Meandering Passage and MacRumors.
I don’t have much to add to the documentation linked above, however, I will say I sympathize with you if you have to install this yourself. I purchased an AirPort card off of Amazon (Airport, not Airport Extreme, mind you), and got frustrated with trying to get the pins to attach. Besides the pins being stubborn, there’s no clear documentation online regarding which pins attach to what–my unit has wires labeled 1, 2, 3, and “BT” (BT was initially attached to the Bluetooth card). Most Airport cards purchased online won’t come with the screws necessary to attach to the motherboard, and my visits to Radio Shack and Best Buy were fruitless. Furthermore, online documentation on which wires to use runs the gamut.
I shamefully took the unit to an Apple-certified Best Buy and paid them $40 to install it. The tech told me that “BT” should attach to the Bluetooth card, and wires #1 and #2 should attach to the Airport card (which made sense since #1 was clearly longer than the others and could easily reach the far side of the Airport card). Wire #3 was for a different airport card with a third port, and wasn’t necessary for my unit.
I took the Mac Pro home, fired it up, and immediately noticed that the wireless signal was very temperamental. I popped the lid and tried every combination of connections to no avail (BTW, I found the pins became increasingly easier to attach after multiple tries. Ultimately, I found that using my flathead screwdriver firmly, but carefully, I was able to quickly attach the pins). I placed wires #1 and #2 back onto the Airport card, since I figured an Apple-certified tech knew what they were talking about.
Ultimately, what I discovered was that my wireless router’s position made a huge difference between 1 bar and 5 bars of signal. This is a far cry from my G5, which had a wireless antenna, though it makes sense, since wireless signals bounce off of metal, and the Mac Pro case is, well, all metal.
Obviously, I can’t say this will work for everyone, but hopefully it’ll shed some light for those with a similar problem.