Apple Thunderbolt Ethernet Adapter: A Mini Marvel

As soon as I saw the announcement of the next generation MacBook Pro with Retina display, I knew I needed to have one. I switched from a 15 inch MacBook Pro to a 13 inch aluminum unibody model last year, but I missed the high-resolution display. Since there were no major feature omissions apart from Gigabit Ethernet, I decided to buy the new model.

While purchasing the new MacBook Pro, Apple asked if I wanted to add a Thunderbolt to Ethernet Adapter for just $29. Intrigued, I added it to my basket. How could Apple produce such a compact and inexpensive Thunderbolt adapter? I assumed it was just a USB device, or leveraged an onboard Ethernet chip in the MacBook Pro.

I was wrong: The Apple Thunderbolt Ethernet Adapter really is a full PCI express device, complete with its own Ethernet controller! This is easily the smallest and cheapest Thunderbolt peripheral to date, and suggests a bright future for similar devices in the future.

Where Are All the Thunderbolt Peripherals

In just over a year of availability, Thunderbolt peripherals have been scarce. I have talked to many of the companies that produce (or wish to produce) Thunderbolt peripherals, and all sing the same refrain: Official Intel Thunderbolt chips remain scarce and expensive. This makes it difficult to produce Thunderbolt peripherals.

Then there is the scarcity and expense of Thunderbolt cables. This will change shortly, as third parties come up to speed with copper and optical Thunderbolt cables compatible with Apple systems. But even then, Thunderbolt cables will remain in the near-$50 price range.

One must also consider the physical size of Thunderbolt peripherals to date. Although Thunderbolt is simple to add to a PCIe reference design, the chip itself is so large it is challenging to design a compelling peripheral. This is why even the smallest Thunderbolt devices are fairly chunky and many are downright porky!

These factors have served to slow the adoption of Thunderbolt, even among Apple-loving media professionals. The cheapest Thunderbolt peripheral today is about $150, including the cable.

The Thunderbolt Ethernet Adapter Dissected

It seems that none of the reviews of the new MacBook Pro or MacBook Air give much attention to the tiny Thunderbolt Ethernet Adapter. This is a shame, because it just might be one of the most revolutionary elements of the whole announcement.

Knowing the reality of Thunderbolt peripheral construction, I assumed Apple was playing a trick with the tiny and inexpensive Thunderbolt Ethernet Adapter. Perhaps it used the USB 2.0 capability of DisplayPort, making it no different from Apple’s existing USB Ethernet Adapter. Or perhaps it was a dumb transceiver that leveraged the onboard Broadcomm Ethernet chip inside the MacBook Pro.

These thoughts were dashed as soon as Apple released a software update allowing the Thunderbolt Ethernet Adapter to be used with any existing Thunderbolt-equipped Macintosh computer. It would be a neat trick indeed if Apple had planned ahead that far for some clever hack!

Indeed, a tear down of the Thunderbolt Ethernet Adapter by Hardmac shows that it is in fact a full-fledged Thunderbolt peripheral! How did Apple do it?

The Thunderbolt Ethernet Adapter includes the standard Thunderbolt cable transceiver as well as a previously unknown Broadcomm Ethernet controller. It is indeed a full PCI express device, as confirmed by System Information in Mac OS X.

If there is a trick here is that Apple is not using Intel’s Thunderbolt-to-PCIe chipset. Instead, it appears that the Broadcom chip is directly connected to the Thunderbolt cable, a previously unknown configuration. It is not clear how Apple managed this. Perhaps the BCM57762 controller includes some special Thunderbolt logic. Perhaps one of the smaller unidentified chips does that hard work. Or perhaps it’s not necessary to include the Intel Thunderbolt controller in every peripheral after all!

Implications for Future Thunderbolt Peripherals

Regardless of the method, Apple has succeeded in producing a remarkably inexpensive and compact Thunderbolt peripheral. The Thunderbolt Ethernet Adapter is substantially less expensive than a bare Thunderbolt cable alone! Whatever Apple has done, they have produced the world’s most accessible Thunderbolt peripheral.

Apple has already promised a Thunderbolt FireWire controller later this month, and I would not be surprised to see additional compact Thunderbolt peripherals released in the future. Thunderbolt to USB 3.0 would be a godsend for owners of 2011 Macs, for example.

Apple is unlikely to address other markets (eSATA, P2 cards, Fibre Channel, etc.) but their design for the Thunderbolt Ethernet Adapter shows that third parties do not necessarily need to include the entire Intel chipset in their devices. I would love to see a compact, half-priced Seagate GoFlex adapter, for example.

Stephen’s Stance

Even if no additional compact and inexpensive Thunderbolt peripherals are ever produced, the Thunderbolt Ethernet Adapter and forthcoming Thunderbolt FireWire Adapter are a godsend for MacBook Pro Retina and MacBook Air buyers. But if others can follow Apple’s lead and produce compact, inexpensive Thunderbolt peripherals, the future looks bright indeed.

Teardown image courtesy of Hardmac