Technology Background

ASUS sent over its upcoming USB 3.1 expansion card and a test device to help us measure excitement for USB 3.1.

Just over a week or so ago Allyn spent some time with the MSI X99A Gaming 9 ACK motherboard, a fact that might seem a little odd to our frequent readers. Why would our storage editor be focusing on a motherboard? USB 3.1 of course! When we visited MSI at CES in January they were the first company to show working USB 3.1 hardware and performance numbers that we were able duplicate in our testing when MSI sent us similar hardware.

But ASUS is in this game as well, preparing its product lines with USB 3.1 support courtesy of the same ASMedia controller we looked at before. ASUS has a new revision of several motherboards planned with integrated on-board USB 3.1 but is also going to be releasing an add-in card with USB 3.1 support for existing systems.

Today we are going to test that add-in card to measure ASUS' implementation of USB 3.1 and see how it stacks up to what MSI had to offer and what improvements and changes you can expect from USB 3.0.

USB 3.1 Technology Background

Despite the simple point denomination change in USB 3.1, also known as SuperSpeed+, the technological and speed differences in the newest revision of USB are substantial. Allyn did a good job of summarizing the changes that include a 10 Gbps link interface and a dramatic drop in encoding overhead that enables peak theoretical performance improvements of 2.44x compared to USB 3.0.

USB 3.1 is rated at 10 Gbps, twice that of USB 3.0. The little-reported-on nugget of info from the USB 3.1 specification relates to how they classify the raw vs. expected speeds. Taking USB 3.0 as an example, Superspeed can handle a raw 5Gbps data rate, but after subtracting out the overhead (packet framing, flow control, etc), you are left with ~450MB/s of real throughput. Superspeed+ upgrades the bit encoding type from 8b/10b (80% efficient) to 128b/132b (97% efficient) *in addition to* the doubling of raw data rate. This means that even after accounting for overhead, Superspeed+’s best case throughput should work out to ~1.1GB/s. That’s not a 2x speed improvement – it is actually 2.44x of USB 3.0 speed. Superspeed+ alright!

ASUS has done some additional work in this area, as they did with USB 3.0, to enable UASP and Turbo Modes for its own USB 3.1 implementations. Turbo Mode is an optimized form of the standard BOT transfer mode (that can only handle one request at at time) that improves device read speeds by adopting a streaming architecture eliminating much of the round trip communication time. This can be run on all devices that support USB 3.0/USB3.1 and SCSI commands and isn't restricted to devices with USB Attached SCSI Protocol (UASP) support.

UASP will still provide the best performance for USB 3.1 devices with nearly all of the delay of command phases being removed and a multi-tasking aware architecture that is capable of handling multiple file transfers at the same time. Much like native command queuing (NCQ) helped improve overall performance for SATA, UASP continues to improve USB experiences.

ASUS enables the activation of UASP and Turbo transfer modes as a part of its AI Suite software shipped with its motherboards. The latest iteration will have the option for "USB 3.1 Boost" and you can speed up your USB 3.1 data transfers with the click of a single icon. In our performance results you will be able to see how this early iteration of USB 3.1 Boost works.

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