USB has emerged as the primary interface of choice for transferring data from computing platforms to external storage devices. Thunderbolt has traditionally been considered a high-end alternative. However, USB has made great strides in the last decade in terms of supported bandwidth: from a maximum speed of 5 Gbps in 2010, the ecosystem has moved on to devices that support 10 Gbps in 2015. By the end of ‘ last year, we saw retail availability of 20Gbps support with USB 3.2 Gen 2×2 on both host and device sides. Almost a year later, how is the ecosystem shaping up in terms of future potential? Are the Gen 2×2 devices currently available in the retail market up to their billing? What can consumers do to take advantage of the standard without spending too much? Western Digital recently launched SanDisk Extreme PRO Portable SSD v2 with USB 3.2 Gen 2
The USB Implementers Forum (USB-IF) has worked hard to introduce new features to the world of USB – over the past five years or so, we’ve seen the emergence of Type-C and numerous upgrades to the same USB standard. USB4 has made a lot of news recently (thanks to its implementation in Intel’s Tiger Lake, as well as the fact that Intel has lent its high-performance Thunderbolt 3 specification to USB4). However, this article deals with the most recent previous specification update: USB 3.2 Gen 2×2.
USB 3.2 Gen 2×2 (or SuperSpeed USB 20 Gbps) – A brief history
In mid-2017, USB-IF announced USB 3.2 to bring 20Gbps bandwidth support to the Type-C ecosystem. Type-C supports two sets of high-speed differential pairs. Only one set is used for traditional 10Gbps operation (in USB 3.2 Gen 2), with the other set used to support alternative modes such as DisplayPort. USB 3.2 Gen 2×2 allows this set to be used for data transmission as well (when alternative modes are not needed). This doubled the available data bandwidth to 20 Gbps. A year later, ASMedia demonstrated a PHY for the 2×2 operation. At MWC 2019, USB-IF has made public the branding strategy for the different versions of USB 3.2: SuperSpeed USB for USB 3.2 Gen 1 (5 Gbps), SuperSpeed USB 10 Gbps for USB 3.2 Gen 2 and SuperSpeed USB 20 Gbps to USB 3.2 Gen 2×2. This was followed by the announcement and demonstration of the ASMedia ASM3242 Gen 2×2 controller for host and the ASMedia ASM2364 Gen 2×2 to PCIe (NVMe) controller for devices at Computex 2019. On the same show, Phison also announced a USB 3.2 Gen a chip single 2×2 / NAND flash controller, PS2251-17.
Premium motherboards with integrated USB 3.2 Gen 2×2 ports started appearing towards the end of 2019 with the introduction of the AMD TRX40 chipset, followed later by the Intel Z490 cards. All of these cards enabled the function using the ASM3242 controller. Manufacturers have also launched standalone PCIe 3.0 x4 expansion cards to equip older PCs with USB 3.2 Gen 2×2 (SuperSpeed USB 20 Gbps) ports. On the client device front, initial demonstrations were carried out with USB 3.2 Gen 2×2 enclosures equipped with PCIe 3.0 x4 M.2 NVMe SSDs. Some of these containers have made it to the retail market. Vendors like Western Digital and Seagate have also released external SSDs that support USB 3.2 Gen 2×2 standard over the past 12 months.
Enter the USB 3.2 Gen 2×2 ecosystem
Consumers looking to step into the USB 3.2 Gen 2×2 ecosystem can choose to build a PC with one of the TRX40 or Z490 cards that support SuperSpeed USB 20 Gbps. Building a new PC is only an option for a few: for a standard interface to take off, consumers must have the port in a standard PC or have PCIe expansion cards that can be plugged into older systems. GIGABYTE was one of the first tier one vendors to announce such a card: the GIGABYTE GC-USB 3.2 GEN 2×2. However, the card has yet to be available for retail purchase.
AbleConn PEX-UB159 and ORICO PE20-1C
The options currently available for adding a USB 3.2 Gen 2×2 port to systems that do not have one are listed below:
Yottamaster C5 and Silverstone ECU06
All of these require a spare PCIe 3.0 x4 expansion slot in the computer. An interesting aspect to note is that Silverstone ECU06 and AbleConn PEX-UB159 do not require any external power. For reasons we haven’t bothered to investigate, ORICO and Yottamaster cards require external power supplied via a SATA power connector. This may be relevant on systems that do not have a spare SATA power connector (as described in the next section). The Yottamaster C5 and the ORICO PE20-1C both appear to use the same PCB, with only the branding on the bracket being different. Also, the PE20-1C product label is printed on the C5 PCB. This is enough evidence to infer that they both come from the same factory line using the same PCB design.
From a device point of view, one of the cheapest ways to adopt USB 3.2 Gen 2×2 remains the purchase of an appropriate enclosure and compatible SSD:
Pairing any of the above with a high-end NVMe SSD like SK Hynix P31 (1TB / $ 135) or WD Black SN750 (1TB / $ 150 or 2TB / $ 310) should result in a fast external SSD SuperSpeed USB 20 Gbps for approximately 20 ¢ / GB. Note that the SSDs mentioned here are specifically the ones that consistently maintain 1.5GBps + direct-to-TLC writes without a significant premium.
The simplest solution is to buy a commercially available external SSD. There are three options currently on the market, specified here in order of retail availability date:
- Western Digital’s WD_BLACK P50 (500GB for $ 134, 1TB for $ 232, and 2TB for $ 350)
- Seagate FireCuda Gaming SSD (500GB for $ 200, 1TB for $ 271, and 2TB for $ 485
- Western Digital’s SanDisk Extreme PRO v2 Portable SSD (2TB for $ 380)
The SanDisk Extreme PRO Portable SSD v2 line will also have a 1TB model, but won’t be available in retail until the end of the year.
Unless you step up to the high end of the capacity line with the 2TB models, the cost-per-GB (greater than 20 ¢ per GB) metric is simply not competitive compared to the 10Gbps SuperSpeed USB external SSDs that have conquered the market in the past two years. At the point of 2TB capacity, excellent external SSDs of this type are available for less than 15 ¢ per GB, while the maximum the three families above can offer is 0.175 ¢ per GB. As adoption increases, the price should drop, but right now there’s no denying there’s a premium. Is it worth it? We examine the components selected from the previous list in an attempt to find the answer.
The test devices
Western Digital had tried a test unit of the WD_BLACK P50 (1TB version) earlier this year, but I had placed it at the bottom of my review queue for a couple of reasons. For starters, none of our direct connect storage testbeds were compatible with SuperSpeed USB 20 Gbps. The other reason was that the WD_BLACK P50, despite its large retail launch, appeared to be more of a tech demonstration product, with the ecosystem for SuperSpeed USB 20 Gbps still in its infancy. Last month, Western Digital doubled its target of the USB 3.2 Gen 2×2 device market with the launch of the SanDisk Extreme PRO v2 portable SSD. A review sample was also provided along with the SanDisk Extreme Portable SSD v2, which was analyzed in detail last week.
Having two Gen 2×2 devices in hand, we felt the standard was gaining ground in the market. To get started with the review, we reached out to a couple of the aforementioned expansion card manufacturers and Yottamaster was the first to respond with a retail sample of the C5 expansion card.
The rest of the review details the steps required to set up an appropriate test bed for evaluating USB 3.2 Gen 2×2 devices, followed by a discussion of the features and characteristics of the WD_BLACK P50 and SanDisk Extreme PRO Portable SSD v2. Provides a look at the performance numbers for various workloads, both synthetic and real, as well as accelerated playback of access tracks. As usual, we also explore worst-case consistency for typical DAS workloads, thermal performance, and power consumption numbers. In the last section, we provide some concluding remarks as we touch on the outlook for the USB 3.2 Gen 2×2 (SuperSpeed USB 20 Gbps) standard.