2016 Macbook Pro snafu highlights the mess with USB Type-C


— 4:26 PM on November 9, 2016

The recent advent of USB Type-C reversible connectors spelled an end to plug-flipping finger gymnastics and ushered in a new era of universal compatibility along with the ability to pass video signals and up to 100W of juice over a single cable. All of this should work seamlessly, too. Right? Not quite, according to reports gathered by ExtremeTech. It seems the new Macbook Pro isn't compatible with the majority of existing Thunderbolt 3 peripherals in spite of all the USB Type-C-ness involved. This situation highlights what's a brewing mess with USB Type-C that's only going to get worse and likely to leave consumers and technicians fuming.


One USB port to bring them all and in the darkness bind them

The Macbook Pro's issue stems from the fact that it uses a recent version of a Texas Instruments chip that handles Thunderbolt power and mode negotiation. The newer chip is the TPS65783, and existing Thunderbolt 3 devices use the TPS65982. By itself, the new chip isn't an issue, but macOS apparently expects all connected devices to use the "83" model, thereby failing to connect with any that use the older chip. ExtremeTech believes this has to do with the fact that support for the new chip is fairly recent, even within Intel's own Thunderbolt 3 SDK. The site also drilled down through both the 82 and 83 chips' data sheets and couldn't find anything that would explain this incompatibility.
 
Because of this problem, peripheral vendors Plugable and Akitio have published lists detailing which of their wares are compatible with Apple's latest machine. While upcoming Thunderbolt 3 devices will almost certainly be compatible, buyers who got one of the recent Macbook Pros hoping to use existing or recently-bought TB3 peripherals may be stuck on land.


Source: Stephen Foskett blog

While the situation with the Macbook Pro is unfortunate, it only highlights the tip of the problems with the USB Type-C standard. To wit, a Type-C port may pass data signals ranging from the 480Mbps of the USB 2.0 protocol all the way to Thunderbolt 3 and its 40Gbps. The protocol also allows for passing video signals and up to 100W of power, too. The problem is that unlike USB 2.0, all of these characteristics are wholly dependant on distinct components: control chips, cables, and even software.

Now, should any of those components fail, there will be problems. Right now the component that's failing the most are the cables. One would think that a Type-C cable is a simple, known quantity. One would be dead wrong. A quick look at store listings for Type-C cables shows a multitude of wires that look the same but are wildly different. Some support a speed of 480MBps, some can hit 10Gbps, a few can be used for Thunderbolt 3. A cable may carry up to 100W of power, or it may fry a laptop. Looking to use an external display over USB Type-C? Better pick the right cable among all those same-looking ones. Blogger Stephen Foskett has some choice words about the entire situation, and it makes for an interesting read.

Then there are the power delivery issues, as if incompatibility wasn't a big enough problem. The issues first came to light when a Google engineer lost his Pixel C convertible to a bad USB cable. There have been subsequent reports of similar problems around the world, and the situation has gotten so dire that the internet collective took to creating a spreadsheet detailing the characteristics and reliability of Type-C cables. One thing's for sure—the situation is likely going to get worse before it improves any.

 
   
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