Gigabyte P55A Boards USB3, SATA3 Issues Analysis

usb3sata3 gb 1 Gigabyte P55A Boards USB3, SATA3 Issues Analysis

Hardware.info has some information about the PCIe bottleneck issues on Gigabyte P55A motherboards supporting USB3 and SATA3. There are 3 scenarios you could face using that board. One, your graphics card will run at half the PCIe bandwidth (x8) if you use USB3 or SATA3. Two, if your graphics card run at full speed (x16) or if you are on Crossfire/SLI (x8,x8), USB3 and SATA3 will run at half speed. Third, if you are running 3 graphics cards like tri-Crossfire or SLI+PhysX, you can’t use x1 slots or the eSATA at all.

Hardware.info has some information about the PCIe bottleneck issues on Gigabyte P55A motherboards supporting USB3 and SATA3. There are 3 scenarios you could face using that board. One, your graphics card will run at half the PCIe bandwidth (x8) if you use USB3 or SATA3. Two, if your graphics card run at full speed (x16) or if you are on Crossfire/SLI (x8,x8), USB3 and SATA3 will run at half speed. Third, if you are running 3 graphics cards like tri-Crossfire or SLI+PhysX, you can’t use x1 slots or the eSATA at all.

usb3sata3 gb 1 Gigabyte P55A Boards USB3, SATA3 Issues Analysis

The first photo is showing the scenario of the PCIe bandwidth allocation between the graphics card and the USB3/SATA3 chips. Lynnfield CPUs have 16 PCIe 2.0 lanes onboard while the P55 PCH has 8 PCIe 1.0 lanes and USB3 and SATA3 each takes up 1 PCIe 2.0 lanes. To make USB3 and SATA3 run at their full speed, they need to be on PCIe 2.0 lanes. Therefore, the graphics card has to run at half speed (x8) so that USB3/SATA3 chips can get 1 PCIe 2.0 lane each and remaining 6 PCIe 2.0 lanes are wasted. The performance impact of the graphics card running at half speed will come when you are having a high end graphics card with all eye candies enabled.

usb3sata3 gb 2 Gigabyte P55A Boards USB3, SATA3 Issues Analysis

The second photo is showing the scenario when you want to run the graphics card at full x16 speed leaving none for the USB3/SATA3 chips. Therefore, the USB3/SATA3 chips will have to take 2 PCIe 1.0 lanes from the P55 PCH. The performance impact is that the USB3 and SATA3 devices will be running at half speed like the USB2/SATA2.

usb3sata3 gb 3 Gigabyte P55A Boards USB3, SATA3 Issues Analysis

The third photo shows what happens if you want Crossfire/SLI and the graphics cards run at x8/x8 speed and similarly, USB3/SATA3 runs at half speed.

usb3sata3 gb 4 Gigabyte P55A Boards USB3, SATA3 Issues Analysis

The last photo depicts the scenario when you are running triple Crossfire or SLI+PhysX where the first two x16 PCIe slots get 8 lanes from the CPU each and the last x16 PCIe slot get 4 lanes from the P55 PCH leaving only 4 lanes. And out of 4 lanes, 2 lanes are used for Gigabit LAN chips, leaving only 2 lanes for eSATA, USB3, SATA3 controllers as well as 2 PCIe x1 slots which is obviously not enough. As such, eSATA port and the 2 PCIe slots will be disabled.

To solve the problem, manufacturers will need a PLX switch chip but that costs an additional $20-25. Gigabyte did that to beat its competition to release a USB3/SATA3 board out fast and at a lower price. Consumers have to right to know the issues they could possibly face when getting the Gigabyte P55A boards and whether the performance scarifice is worth it if you are getting it right now.