In case you are an owner of the motherboard Gigabyte GA-990FXA-UD3 AM3+, depending on your kernel and BIOS versions, it is possible that you encounter the very same issues as I did. Don't worry, it was just a little bit tricky to find the fix but after that everything works flawlessly.
I currently run Arch Linux with a kernel version 3.12.3. The issues with this motherboard were that USB ports didn't work properly nor Ethernet. Many error messages related to IOMMU were also thrown to
The solution is quite simple. Enable from the BIOS the
IOMMU device and append to your kernel boot parameters
One more issue was the overheating of the VRM heat sink. Just make sure that the heat sink that covers this component is ventilated enough. If not, you will see how the temperature of this heat sink rises and under heavy load the CPU frequency starts jumping between its maximum and minimum. Once the appropriate ventilation is in place, the CPU can work at its maximum frequency for long periods of time.