Controller Conundrum: USB 3.0 & SATA 6G
Now that we've discussed the board's layout and design, let's take a closer look at two of its defining features. Gigabyte has put a major push behind USB 3.0 and SATA 6G, but first-generation controllers are often plagued with compatibility issues or simply aren't as fast as later iterations.
Below is a block diagram of the UD3R's Marvell 9128 SATA 6 controller. Of the four SATA 6 controllers Marvell currently has available, the 9128 is the nicest; it supports RAID, 128-bit/256-bit AES encryption, offers two SATA 6G ports, and an additional PATA port (though Gigabyte isn't using it). Some of you may recall the last-minute discovery of compatibility issues that forced board manufacturers to pull SATA 6G support right before the P55 chipset launched. The problem turned out to be with the 9123's PATA port; Marvell has respun the chip into the 9128, but Gigabyte opted to use a Jmicron controller for PATA support.
The only theoretical shortfall is the controller's available bandwidth. The Marvell 9128 connects to the system via a single PCIe x1 link capable of transferring 400MB/s. That's only 67 percent of the theoretical peak of the SATA 6G interface, but it's far more bandwidth than any conventional hard drive can saturate, even in RAID 0. SSD owners don't need to worry, either. No current single SSD can sustain read/write speeds much above 250MB/s, it's far from certain that even a pair of top-end drives in RAID 0 would actually encounter a significant bottleneck.
Next up we've got USB 3.0, courtesy of NEC's PD720200 controller. Here's the simplified block diagram (if you want to see the more detailed version, you can read about it here):
What we see above is that the NEC chip contains both a USB 3 and a USB 2 controller with both controllers interfaced to both ports. What the rather confusing intersection of arrows shows is that any combination of USB 2 and USB 3 devices can be attached without the need to worry about interface speeds. Need to combine a USB 2 and a USB 3 device on those two ports? No problem.
This sort of flexibility is often something that early adopters sacrifice in exchange for new technology, and it's to NEC's credit that their implementation avoids compatibility headaches. Those of you planning to use a pair of high-performance external enclosures, however, should be aware that there's a caveat—available bandwidth is shared between all devices. Slower, 2.5" drives may not be affected and may not be capable of saturating USB 3's bandwidth even in tandem.
Power Provisioning Muddies Backwards Compatibility Of USB 3 Devices In USB 2 Ports:
Seagate's BlackArmor 110PS
One other caveat about USB 3 devices in general is the question of how much power modern USB 2 ports can provide. We talked this over with Intel, which indicated that newer, higher-power USB 2 spots are probably those that conform to the USB-IF Battery Charging 1.1 Specification. This update was released in 2007 and refreshed about a year ago.
Unfortunately, it's hard to know which motherboards support it. The modern Core i7 boards we tested can power the Seagate BlackArmor PS110 from any USB 2 port, but one of our own X48 motherboard from Asus can only run the external enclosure from the back ports. Based on this, we don't recommend buying a BlackArmor with the plan to upgrade to USB 3 via controller card at a future date unless you know your motherboard can provide the necessary juice.
With that said, if you know your motherboard can charge an iPad while the device is running, it should also be able to run the external hard drive.