P55A-UD6

The first motherboard we’re looking at is Gigabyte’s GA-P55A-UD6. This motherboard is based on their P55-UD6, only it’s been updated with 333 support. The P55-UD6 was one of the best high-end P55 motherboards of last year. It offered a boatload of connectivity options, and was equipped with really powerful heatpipe cooling. Its most notable feature though was its 24-phase power design, the first motherboard to be equipped with so many phases. The arrival of the board started a power phase arm race with ASUS, who responded with their own 32-phase P55 motherboard.

As we mentioned on the previous page, a Superspeed USB 3.0 controller from NEC is used on the P55A-UD6 board. The controller used is the NEC D720200F1, which is actually used on a wide range of USB 3.0 devices, including controller cards and other motherboards. Meanwhile Marvell’s SE9128 is used for 6Gbit/sec SATA.

The issue is that both of these controllers are PCIe-based devices, both with high bandwidth demands. And Gigabyte relies on the CPU’s integrated PCIe lanes to drive them.


As anyone who’s familiar with the Lynnfield/P55 platform can tell you, PCIe bandwidth is one of the key weaknesses of the platform. To keep costs down (and provide some breathing room for X58), Intel just didn’t equip it with a lot of PCIe lanes; 16 lanes total – just enough for one PCIe graphics card, or two cards running in x8 mode.

Because of this, when the USB 3.0 and 6Gbit/sec SATA controllers are in use, the primary graphics card runs in x8 mode, while the second PCIe graphics slot is disabled. When two PCIe graphics card are running in SLI/CrossFire mode, the USB 3.0 and 6Gbit/sec SATA controllers revert to just 2.5Gb/sec so that both graphics cards can run in x8 mode.

So you’re either going to sap the potential performance of your GPU, or your USB 3.0 and SATA drives.

Fortunately USB 3.0 and SATA 6Gb/sec devices come nowhere close to hitting their theoretical transfer rates. As a result, the performance hit isn’t as bad as it would first appear. In a single GPU configuration, the P55A-UD6 performs comparably to its predecessor in 3D gaming, while it’s doubtful SLI or CrossFire users would be pressing their SATA or USB 3.0 subsystem while also gaming.

Gigabyte knows this is an issue though, which is why they’ve devised the P55A-UD7. The UD7 board features a PLX PCIe bridge, providing an additional 32 PCIe lanes for the USB 3.0 and SATA 6Gb/sec controllers. But that’s not all, as the board also ships with NVIDIA’s NF200 chip, which allows the board to support 3-Way SLI.

No word on how much all this is going to cost though, as the UD7 hasn’t been released yet.