Check Out The Secret High-Tech Circuitry That Controls Apple’s $49 Thunderbolt Cable



As if on cue, the first teardowns of Apple’s Thunderbolt cable have hit the Internet, and prepare to be surprised: that $49 retail price isn’t just the usual Apple tax, but a fair asking price for the advanced circuitry within!

The guys over at iFixIt tore down Apple’s new cable. Amazingly, it’s not just a bunch of copper. Rather, each cable is what is called a “smart” or “Active” cable that contains both circuitry and firmware.

Inside each Thunderbolt cable you’ll find two Gennum GN2033 chips, one in each connector.That’s in addition to 12 other support chips, resistors and electcal components.

What does the Gennum chip do? It’s a transceiver that enables “reliable data transfer at cutting-edge speeds over low cost, thin-gauge copper cables.” Put another way: at data rates above 5Gbps, you need to have chips to adjust for cable attenuation and dispersion properties to maintain a high signal-to-noise ratio.

Here’s the best part of Apple’s Thunderbolt cable: it’s future proof. While the current version uses standard copper, future versions of the Thunderbolt spec call for optical cabling… but when Thunderbolt evolves, your old cables will work just as well as they ever did.

So it seems there’s a lot more going on with Apple’s Thunderbolt cable than it appears at first glance. The only depressing aspect of all of this is that it seems that Thunderbolt cabling will remain extremely dear for awhile, because of the cost of the circuitry within. Don’t expect to pick up a spool of Thunderbolt at Monoprice for pennies on the dollar anytime soon.

  • Tomas

    Seems a shame that the spec isn’t put together well enough so that the electronics are all BEFORE you get to the cable, so they are only bought once, instead of in each and every cable so one buys “active cables” over and over.

    An adaptive interface with the complexity – and electronics – built into the device rather than the cables is, indeed, a more difficult problem, but…

    (The idea would be to have the chips in the device interface and only the few passive components that tell the chip what to do to customize the interface for the particular cable in the cable.)

    (Disclaimer: Retired telco transmission engineer…)

  • 300AShareMakesMeSmile

    Oooh!  Apple Monster cables.

  • Sean Cheesman

    How does the device know how long the cable is?  What type of cable?   By building it into the cable, you take a lot of error control and “guessing” away from the device and allow it to transmit at its full potential.  Let the cable manufacturers ensure that the chips are programmed for their specs.

  • Tomas

    By simply including a few passive devices in the cable connector to tell the chip in the device how long and what type, so that the device chip can can set itself to match the cable.

    Ever notice when an Apple monitor is plugged into an Apple computer how the computer knows the monitor’s specs and adjusts to the proper resolution, etc?

    Simple fixed passive coding from the monitor.

    With Thunderbolt what you have is essentially an active equalizer, and with something like that one can put the “instructions” in the cable and the actual equalizer in the device.

    (Of course doing it this way, with the entire active equalizer in the cable, Apple eliminates having to fight the third party makers of cheap cables, and can lock a customer into only buying cables from Apple – at a profit, of course.)

  • Bob Forsberg

    Is it only me or do I see another betamax thing here vs USB3…USB4.

    2′ cable…. 3′ max? Not many peripherals yet and HDMI is still absent on most Apple products.

  • oriorda

    The price is cheap when you figure what you’re getting. For example, cost/MB/sec.

    As soon as there’s volume, someone will come in with low cost, but even if they do, my guess is serious I/O users will opt for the Apple cables. Why risk problems just to save a few bucks?