Network Card Issue

Having reinstalled OS X from scratch we can initially presume it is indeed a hardware issue. Things to try next are -

• Try the other network socket on the Mac Pro (it has two)
• Try a different network cable
• Try a different network socket

If non of the above help then it may be the chip rather than the socket or cable, in which case as the chip is soldered on to the logic board you would need to look at getting a different network adapter. This could be a USB one or a PCIe one. See the following for examples.

http://www.apple.com/uk/shop/product/MC704ZM/A/apple-usb-ethernet-adapter

http://www.kanex.com/usb3lan

http://www.sonnettech.com/product/prestogigpciepro.html

http://www.sonnettech.com/product/prestogigpcieserver.html

Network Utility (included with Mac OS X) can read out the error counters associated with a particular link to see if it is accumulating errors. There should not be more than an initial small burst, and growing numbers (even very slowly growing) indicate a problem:

If you cannot find it, you may have to chase it down from:

/System/Library/CoreServices/Applications/Network Utility.app

I find it helpful and use it often. It also tells you the actual speed of your Ethernet connections, rather than the configured speed. The other panes include a GUI-faced Ping and many others.

That link states it is running at 100Mbit/sec.

To run at Gigabit speeds, all cables must have all eight wires in them (none may be used for power-over-Ethernet) and all devices must support Gigabit speeds.