USB 3.2 Gen 2x2 State of the Ecosystem Review: Where Does 20Gbps USB Stand in 2020?
by Ganesh T S on October 5, 2020 10:30 AM EST- Posted in
- Storage
- SSDs
- Western Digital
- SanDisk
- ASMedia
- USB 3.2 Gen 2x2
Synthetic Benchmarks - ATTO and CrystalDiskMark
Western Digital claims claims read and write speeds of up to 2000 MBps for both the P50 and the Extreme PRO Portable SSD v2, and these are backed up by the ATTO benchmarks provided below. Unfortunately, these access traces are not very common in real-life scenarios.
| Drive Performance Benchmarks - ATTO |
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On the Haswell testbed, the Extreme PRO v2 hits 1.94 GBps writes, while the P50 manages 1.92 GBps. When connected using the eGFX enclosure to the Thunderbolt 3 port of the Hades Canyon NUC, the writes suffer a significant drop to the 1.4 - 1.5 GBps range, while the drop in the reads is not as drastic - ending up around 1.8 GBps for both of the drives.
CrystalDiskMark, despite being a canned benchmark, provides a better estimate of the performance range with a selected set of numbers. As evident from the screenshot below, the performance can dip to as low as 33 MBps for low-queue depth 4K random reads.
| Drive Performance Benchmarks - CrystalDiskMark |
 |
The sequential reads and writes are more useful from a direct-attached storage viewpoint. Here, we see around 2080 MBps for the Extreme PRO v2, and 2045 MBps for the WD_BLACK P50 as the best-case performance using the Haswell testbed.
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DanNeely - Monday, October 5, 2020 - link
Read the last page of the article. The USB maintainers have decided to make USB4 even more of a garbage fire of confusion than previous versions. USB4-20gb and USB-40gb ports are only required to support 10gb data rates for USB drives (and can count bandwidth to alternate data stream devices, ie parallel video out) toward the total.IMO it's past time to disband the current USB group, and create a new C(ompetant)SB organization to maintain future standards that bans anyone involved in the USB 3.x/4.x nomenclature from membership.
Spunjji - Monday, October 5, 2020 - link
I'm actually inclined to agree. It's gone way, way past being a joke at this stage.Kangal - Tuesday, October 6, 2020 - link
Well, we can always ditch USB3.1 / USB4 as consumers.Instead ask for USB-A (3.0) for legacy support, and then opt for USB-C (TB4) instead. Just say "hell no" to the USB-IF consortium and their broken standards.
Yet, that might be okay for now/per individual, but it's not gonna solve anything in the long run. And even worse, we can't actually do that because there is a lack of options in the market (ie You don't get to choose which ports your device has, you are stuck with whatever option they deem good for you). Tough times.
repoman27 - Monday, October 5, 2020 - link
Stop spreading FUD and read the specs, they're freely available for download. USB4 operates at 20Gbps (Gen 2x2) or 40Gbps (Gen 3x3) but it's a tunneling protocol, i.e. a *totally different* protocol than USB3. Backwards compatibility is mandatory and at least USB3 10Gbps (Gen 2x1) as well USB 2.0 signaling is required. USB 2.0, 3.2 and 4 involve different signaling and different protocols.USB4 supports tunneling of PCIe and DisplayPort packets in addition to native USB packets so that the total bandwidth can be flexibly and efficiently shared. Not bothering to understand this and instead spewing internet outrage helps no one.
repoman27 - Monday, October 5, 2020 - link
D'oh, that should have been "40Gbps (Gen 3x2)".ganeshts - Monday, October 5, 2020 - link
@repoman27's technical explanation is A-OK :) The move to tunnelling is definitely a big step for USB.However, @DanNeely's comment is also correct from a *consumer* viewpoint ; Would a regular non-tech savvy consumer care about tunnelling? If he sees USB4 20Gbps, would it be unfair for the person to expect his USB SuperSpeed 20Gbps device to work to its full potential in it?
All these problems could have been avoided if USB 3.2 Gen 2x2 capabilities were integrated into USB4 as mandatory.
repoman27 - Monday, October 5, 2020 - link
Oh, totally. But on the other hand, if Intel had just included USB 3.2 dual-lane operation in Tiger Lake / Thunderbolt 4, nobody would have realized it was optional, because it would have been supported everywhere one might expect it. I’m afraid that Intel intends to completely forego USB 3.2 dual-lane operation in favor of Thunderbolt.Kevin G - Monday, October 5, 2020 - link
It mainly boils down to USB 3.2 @ 20 Gbit not being the same implementation as USB 4 @ 20 GBit, a very year 2020 problem to have.There is still interoperability between the two but that knocks the speeds down to 10 Gbit. That is noticeable for things like storage doing transfers on fast SSDs etc. From a consumer stand point though, things will still work which I would rank as more important.
I will say that these issues lay with the USB consortium as they've created a mess of specifications that makes it difficult for things to work *as advertised*. Historically they also have needed to crackdown to lazy implementations and bad cables. Give that group a bit of teeth to enforce their spec and things would be far better for consumers today.
repoman27 - Monday, October 5, 2020 - link
Well, at the risk of beating a dead horse, nothing prevents a USB4 host/device from also supporting USB 3.2 20Gbps. It’s just that it’s optional, Intel didn’t include it in Tiger Lake, and I’m not aware of anything on their roadmap that will in the near future.You can choose to blame the USB-IF, Intel, or the fact that Intel pretty much runs the USB-IF. But at this point Intel hasn’t shown us any products containing USB 3.2 20Gbps IP, and without Intel on board, I’m not sure what kind of future that standard has.
Spunjji - Wednesday, October 14, 2020 - link
Makes sense. They've been artificially holding the standard back ever since they decided they'd rather push Thunderbolt over USB 3.