Quick Review, Teardown: “Avoid driving fast card” USB 3.0 Ethernet Adapter

It’s always nice to have a few extra Ethernet interfaces on a computer – sometimes you need to run a software firewall, use a computer as a router, or you just need to sniff some network traffic running to a device for some reverse engineering or testing purposes. With the increased bandwidth of USB 3.0 as compared with USB 2.0, new gigabit USB 3.0 Ethernet devices can be quite good performers.

In need of a few more interfaces, I splurged on the cheapest decent-looking USB 3.0 gigabit Ethernet adapters I could find. For under AU$11 posted, I managed to get one of these:

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Like many Chinese “direct from the factory” bargain basement goods, it’s packaged inside a zip-lock bag with nothing – no documentation, no CD.

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The unit has a most curious and very entertaining public service announcement on its label – “USB 3.0 Avoid driving fast card“. I think it’s a wise message, but … it doesn’t exactly tell us what it is? Maybe some translation software is to blame …

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The underside is pretty plain, with a space for a vendor label that was never applied.

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USB 3.0 one end, Ethernet port with integrated status lights on the other. Doesn’t take a rocket scientist to figure out what this is!

Teardown

What powers this unit? It took a few fingernails to pry the case apart to find out.

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The PCB’s rear has the USB 2.0 connections with their colour codes silkscreened. The board seens to be made by TEAN, and is dated Week 48 of 2015 making it fairly fresh stock. A 25-series 4Mbit serial Flash is used to store the configuration and other data. The board has good isolation around the Ethernet pins.

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The top side reveals it is a Realtek RTL8153. The PCB is marked SYZD-169, version 1.0. The soldering looks decidedly hand-done, but at a decent level. The colour coding of the USB 3.0 lines doesn’t match the silkscreen on this side, so I suspect there may have been an error in the PCB there. A discrete transformer is used – if they had used a magjack, the whole unit could be almost half the size.

Installation and Quick Test

Unlike other adapters with the ASIX chipset, where plugging it in will automatically have Windows download an appropriate driver from Windows Update, this one is a little different.

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At first, it tries to search, but it fails. Nothing is found. But then, a sneaky little surprise appears – it reconnects itself as a CD-ROM drive to deliver the drivers – in this case, it was a 384kB self-extracting 7-Zip file with drivers for Windows XP, Vista, 7, and 8 for both 32 and 64 bit.

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It’s definitely a nice touch – and a good use of 3/4 of the serial flash space – after all, configuration in custom PID/VIDs only take a few bytes rather than kilo-bytes.

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The problem is that these drivers are somewhat out of date – 2013 versions. At least they are enough to get the unit working, so you can get online to update your drivers, avoiding the chicken-and-egg issue with the ASIX units – if you don’t have a connection and you don’t have the CD or a CD-ROM drive to read it with, how do you install the drivers?

The unit itself features many off-load capabilities, and when tested with a file copy from another server, it was capable of sustained ~110MB/s throughput.

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It’s not bad – it’s most of what Gigabit Ethernet is capable of, maybe about 10-12Mb/s shy of it due to USB 3.0 latencies, overheads in the driver, and probably timing issues with my network. Considering it was an SSD to SSD copy, rather than a memory to memory copy, it is definitely respectable performance for a USB 3.0 peripheral.

The one annoyance I found was that sometimes if the driver didn’t pick up and initialize an inserted adapter quickly enough, it would flip over to CD-ROM on its own even though the driver was installed. This necessitated an unplug and replug to solve. I suspect I wouldn’t be relying on this adapter to correctly reconfigure itself after a reboot as things like this could occur, and if you were relying on it for remote access, you’d be locked out until someone unplugged and re-plugged the adapter.

Conclusion

It’s cheap, it’s got a whacky name, and it’s got a rather pedestrian Realtek chipset, but it does what we expect it to at a good price. It does have one quirk – the USB CD-ROM mode which helps you get started also can get in the way if the installed drivers don’t initialize the card quickly enough – so I wouldn’t recommend this as an interface that can be relied on to come up after a reboot every time.

About lui_gough

I'm a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!
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