AMD's chipsets and processors, unlike Intel's, do not support the PCI Express 3.0 interface, which is why motherboard makers didn't bother including the interface in their designs, until now.
ASUS figured that if AMD's chipsets didn't have what it took to run PCI Express 3.0 x 16 slots, it might as well use a specialized chip instead.
The company decided on the PLX-made 48-lane PCI-Express Gen 3.0 bridge chip.
It is this processor that powers two of the four PCI Express slots on the Sabertooth 990FX/GEN3.0 R2.0.
Said slots can be wired in x8/x8 mode, although it is possible to run one alone, in x16 mode.
The other two PCI-E slots are of the normal 2.0 x16 variety, wired directly to the 990FX chipset, rather than the aforementioned PLX 48-lane PCI-Express Gen 3.0 switch.
Truth be told, the PCI-E 3.0 technology is here more for bragging rights than anything else. Though there are a few exceptions, video cards don't actually need the extra bandwidth from the interface. Most can't even use it.
Still, if nothing else, luck favors the prepared. It won't hurt to have PCI-E 3.0 for when NVIDIA and AMD release newer and stronger graphics cards.
The rest of the features on the ASUS Sabertooth 990FX/GEN3.0 R2.0 motherboard are the same, more or less, as on any other high-end AM3+ platform.
Eight SATA 6.0 Gbps ports are present, for instance, as are a couple of eSATA 6.0 Gbps ports, 8-channel HD audio and six USB 3.0 connectors.
ASUS did not say when sales of the Sabertooth 990FX/GEN3.0 R2.0 would begin, although reports
say it will happen very soon. Likewise, there was no hint as to what the price would be when shipments finally began.
In the meantime, more information can be found on the support page, located here