SSUSB + Turbo & SLI Gaming….what???
I wanted to go into a bit more detail on this test. Going back to the quote from Gigabyte above, …”one way is Turbo mode where it uses PCI-E lanes to communicate directly with the CPU for best performance. The other way is through the P55 chipset where it is limited to PCI-E gen 1 speed (2.5Gb/s) – when turbo mode is disabled”… I have seen around the web some concern over this implementation, so I wanted to give some examples over performance with the system bandwidth stressed. My testing is by no means exhaustive, and more investigation may need to be done. Going back to what we know about the Lynnfield architecture is that the PCIe controller is built into the CPU itself, and there is a total of only 16 lanes. That means if you have a single graphics card, it will perform best if it can use all 16 lanes, and if you have dual cards, you’d be running with 8 PCIe lanes to each.
Gigabyte really didn’t want to force users into degrading their graphics performance by only allowing the SSUSB controller to use one of the CPU’s PCIe lanes. Instead, they decided to link it to both the CPU and to the P55 chipset which supports a single PCIe 1.1 lane (2.5Gb/s limited). This is where “Turbo” mode comes in. If you have an external SSUSB SSD and want maximum performance from it, use Turbo mode and the SSUSB controller will use one of the 16 PCIe lanes on the CPU, slightly deteriorating the graphics performance, but allowing maximum throughput to the SSUSB connected devices. If you are more concerned with maximizing your graphics performance, and don’t need the extra SSUSB throughput, or if you have a slower SSUSB device like the HDDs in my testing, turn off Turbo mode, and use all 16 PCIe lanes on the CPU for your graphics cards.
I’ve heard a bit of grumbling that Gigabyte made a bad decision here, but I honestly cannot see a better way to implement this technology, and I applaud Gigabyte for leaving the decision in the hands of the user for deciding what performance should take priority in their system. For those users who do not want to compromise performance for any device, they should be looking at a system based on the Nehalem (X58 & LGA1366) architecture anyway. For a budget friendly system based around P55, this should make everyone happy.
The purpose of my testing here was to show that although no single component of the system is performing with 100% of it’s potential bandwidth, performance is still excellent, and SSUSB is still a massive improvement over USB 2.0!