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Comment by X-Istence | Hacker News Reader

The downside is that the ethernet controller is run over USB. This is what kills performance drastically on the raspberry pi as well. USB is simply not a good protocol to run high speed network traffic over with low latency. The protocol is extremely chatty!

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The Freescale i.MX6 has "native" Gigabit Ethernet: http://www.freescale.com/webapp/sps/site/prod_summary.jsp?co... (that's the single-core part)

The block diagram for the "Tiny cubic mini pc" shows a AR8030/AR8035 between the CPU core and the outside world, that's a Gigabit PHY, not a Gigabit to USB chip, so indeed the native ethernet is used.

Are you sure about that? The block diagram shows an Ethernet PHY connected directly to the SoC, and it appears the i.MX6 has a built-in Ethernet controller.

I am going off the bottom of the page (http://cubox-i.com), where it says it is limited to 470 Mb/sec due to internal busses.

470 Mb/sec sounds too similar to USB 2 to not be USB 2.

Actually did the right thing and looked at the datasheets involved: http://cache.freescale.com/files/32bit/doc/data_sheet/IMX6DQ...

and

http://cache.freescale.com/files/32bit/doc/errata/IMX6DQCE.p...

This seems to be an internal limitation of the bus. It is not run over USB! This means it will most likely reach that 400 Mbps claimed in the errata:

Quote:

ERR004512 ENET: 1 Gb Ethernet MAC (ENET) system limitation Description: The theoretical maximum performance of 1 Gbps ENET is limited to 470 Mbps (total for Tx and Rx). The actual measured performance in optimized environment is up to 400 Mbps. Projected Impact: Minor. Limitation of ENET throughput to around 400 Mbps. ENET remains fully compatible to 1Gb standard in terms of protocol and physical signaling.

I dont think it is actually USB2, just a similar speed bus. But it is a bit annoying - some tests here http://boundarydevices.com/i-mx6-ethernet/

If you want to really move network packets in embedded computing environments, you need a processor oriented a little differently, the iMX6 is an embedded multimedia processor, and for my 2cents, it's architected to do that job pretty nicely. There's trade between power savings and a faster peripheral bus. The Gigabit ethernet running at those specs I'm guessing pushes streaming video nicely (I'm guessing sized for about enough bandwidth for a compressed 1080p 60fps stream with a little bit of margin).

It's still a limiting factor, especially for someone trying to build a media server out of it for example like some people were already considering home NAS's...

That's actually rather unfortunate—the original Cubox (/pro) based on the Armada 510/Dove has a GigE PHY which is completely capable of ~1000 megabits.

Hmm, I've noticed this on the Raspberry Pi, but I'm curious, do you know if this is a problem for desktop PCs as well? I recently built a mini-ITX PC sort of for fun as a change of pace and then realized that the apartment where I'm moving makes it somewhat annoying to run ethernet cables to my router, so now I'm looking at USB wifi dongles. The annoying thing is mini ITX boards generally only have one PCIe slot, and as it turns out my PC is barely smaller than my previous mATX PC (Bitfenix Prodigy is actually pretty big for mini ITX, which I didn't realize). The annoying thing is that there were mini ITX boards with built in wifi but I figured I wouldn't need it so I decided to save ~$50, but in hindsight I should have just gotten it.

USB 2 will work just fine for Wifi dongles. You are not going to get anywhere near speeds high enough to saturate USB 2 with Wifi.

With GigE adapters for USB 2 though, it is pretty bad.

That is the biggest killer for using the Pi for any real file serving needs. If you have it reading from a USB HD and transferring a lot over the network it's pretty slow. You can tweak it a bit to improve the speeds, but it's really not designed for it.

Nice to see some models of this support sata.

If you're just streaming media, it's fine.

I've been using an apple usb ethernet adapter on my Acer Revo for about 3 years after the built in ethernet port died.

I can get 350mbit-ish out of the Dreamplug - do you know of any small devices with two Ethernet ports that can do better? I'm looking to upgrade.

So it's USB 2.0? That's half duplex anyway, so no way are you going to get 470mb/sec out of it. Max is probably around 423.

It is actually not, I was wrong. It is an internal limitation on the bus that limits it to about 400 Mbps by default, some people have been able to squeeze a little more out of it. After that point though all kinds of issues start appearing. See the links provided in the discussion below.

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