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Everything You Need To Know About Thunderbolt

Everything You Need To Know About Thunderbolt
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A year after its debut on Apple platforms, Thunderbolt is finally available for PCs. Both fast and scalable, the technology’s 10 Gb/s connectivity and potential for external graphics promises to inspire innovation. But is it ready for prime time?

Mac and PC users are never going to agree on which platform has the best operating system. But when it comes to hardware, though, the PC world has an undisputed advantage. We have a lot more choice when we pick our processors, graphics cards, and motherboards. If you're using a Mac, you have to wait for Apple to add driver support for the device you want (if it ever happens at all).

Thunderbolt violates the rule that PCs get the coolest technologies first. For almost a year, Mac users have been enjoying the Thunderbolt, which was developed by Intel, because of collaboration from Apple. Power users with PCs were forced to sit and wait, though a dearth of client devices made it more tolerable to watch the Mac guys get their hands wet with Thunderbolt. 

MSI recently released the first available motherboard with Thunderbolt support, its Z77A-GD80, ending Apple’s monopoly on what could be considered the coolest interface since the original USB standard. The platform we received is essentially identical to the Z77A-GD65 we reviewed in Six $160-220 Z77 Motherboards, Benchmarked And Reviewed, aside from a 10 Gb/s Thunderbolt port on the rear I/O panel (replacing DVI output), along with a new 14-phase voltage regulator.

If you aren't yet familiar with Thunderbolt or its implications, we definitely believe that the technology is an interface you're going to want on the next system you put together, even if the ecosystem of compatible devices remains fairly small today. 

Of course, Thunderbolt is a name for an Intel initiative originally code-named Light Peak—an optical physical layer used to connect peripherals. Back when Intel first showed off its Light Peak project at IDF 2009, it was thought that optical would enable 10 Gb/s throughput. However, a version employing copper wiring turned out better than expected, allowing Intel to drop costs and deliver up to 10 W of power to attached devices.

The big objection from most enthusiasts is going to be that we already have USB 3.0 showing up as a value-added extra in AMD and Intel chipsets. Why do we need to pay for yet another interface? After all, at 5 Gb/s, a third-gen USB port is almost able to accommodate the peak performance of a modern SSD. Thunderbolt isn't just another peripheral interface, though. It combines DisplayPort and PCI Express into a serial data stream, enabling very powerful connectivity combinations (along with innovative product ideas like MSI's GUS II).

Manufacturers have toyed with USB-based graphics expansion over the years, but none truly succeeded because USB’s unique command set simply wasn't designed to facilitate high-performance graphics I/O. However, Thunderbolt’s low-latency/high-bandwidth interface is, however, making it a robust transport technology with extremely accurate time synchronization support that's ideal external video and audio devices.

How Does Thunderbolt Work?

Systems with Thunderbolt controllers will attached them one of two ways: either it's attached directly to PCI Express links originating from a Sandy or Ivy Bridge-class processor, or it derives connectivity from a Platform Controller Hub's available PCIe.

We suspect that, on the desktop, most motherboard vendors will hook up through the PCH in order to avoid monopolizing processor-based lanes, which are generally needed for add-in graphics. Such a configuration does open up the potential for a bottleneck, since the DMI connection between processor and chipset is theoretically good for around 2 GB/s of bi-directional throughput. If you have a lot of SATA-attached storage cranking away, it's conceivable that the maximum performance of Thunderbolt could be constrained.

In the image above, you can see that DisplayPort data routes between the Thunderbolt controller and the PCH's Flexible Display Interface, since that's where display connectors attach. The FDI is its own pathway, specifically reserved for carrying display information, and it does not impact the bandwidth available through DMI 2.0.

PCIe and DisplayPort signals enter the Thunderbolt controller separately, are multiplexed, travel through a Thunderbolt cable, and are de-multiplexed at the other end.

Thunderbolt requires active cables, which is why they're so expensive (in the $50 range). Each cable end sports two tiny, low-power Gennum GN2033 transceiver chips that are responsible for boosting the signal passing through to enable 10 Gb/s data rates over runs as long as three meters. 

Originally, Thunderbolt was going to be enabled using an optical physical layer and optical fiber cabling. But Intel discovered that it could achieve its 10 Gb/s per channel target at a lower cost using copper wiring. Plans for an optical-based implementation are still on the table, and we expect to see optical cables enabling even longer-distance connections in the future. As we already mentioned, though, copper cabling delivers up to 10 W of power to attached devices. When optical cables do emerge, attached devices will require their own power supplies.

Despite Thunderbolt's many unique attributes, the interface shares certain capabilities with other technologies. For example, it supports hot-plugging. And, like FireWire, it is designed to work in daisy chains. Machines that come armed with Thunderbolt will either include one or two ports, each supporting up to seven chained devices, two of which can be DisplayPort-enabled monitors. So, you end up with the ability to attach:

  • Five devices and two Thunderbolt-based displays
  • Six devices and one Thunderbolt-based display
  • Six devices and one display via mini-DisplayPort adapter
  • Five devices, one Thunderbolt-based display, and one display via mini-DisplayPort adapter 


Of course, daisy-chaining requires that each device (except for the last one) has two Thunderbolt ports. So, when you attach a display that doesn't have a Thunderbolt port, necessitating a mini-DisplayPort adapter, or only has one port, there is no way to pass the signal on to the next device in the chain. As such, displays go to the end when you're linking multiple components.  

The Thunderbolt connector itself is physically compatible with mini-DisplayPort, so turning the connector into a display output is particularly easy.

Are there caveats to putting PCIe and DisplayPort data on the same cable? In theory, no. Apple and Intel resolved early display quality issues encountered on early hardware through a firmware update in 2011. The interface employs two data channels, each capable of pushing 10 Gb/s in each direction. The solution used one channel for device I/O and the other for display signaling. Even still, we cite 10 Gb/s as Thunderbolt's official spec, since performance is not additive.

Display 68 Comments.
Top Comments
  • 22 Hide
    shoelessinsight , June 12, 2012 4:52 AM
    Active cables are more likely to have defects or break down over time. This, plus their high expense, is not going to go over well with most people.
  • 21 Hide
    mayankleoboy1 , June 12, 2012 4:35 AM
    thunderbolt will fail after external PCIE standard is implemented
  • 19 Hide
    Pyree , June 12, 2012 4:23 AM
    I was really hoping to see some eGPU benchmark. Oh well, I guess I have to wait.
Other Comments
  • 19 Hide
    Pyree , June 12, 2012 4:23 AM
    I was really hoping to see some eGPU benchmark. Oh well, I guess I have to wait.
  • 21 Hide
    mayankleoboy1 , June 12, 2012 4:35 AM
    thunderbolt will fail after external PCIE standard is implemented
  • 15 Hide
    mayankleoboy1 , June 12, 2012 4:36 AM
    for more insight of thunderbolt fail and Intel's lying :

    http://semiaccurate.com/2012/06/06/intel-talks-about-thunderbolt/
  • 22 Hide
    shoelessinsight , June 12, 2012 4:52 AM
    Active cables are more likely to have defects or break down over time. This, plus their high expense, is not going to go over well with most people.
  • 5 Hide
    A Bad Day , June 12, 2012 5:39 AM
    Looks like I'm going to steer clear of Copperpeak for my future build.
  • 16 Hide
    GI_JONES , June 12, 2012 5:43 AM
    Cost is going to kill this.
  • 12 Hide
    mayankleoboy1 , June 12, 2012 6:25 AM
    ^
    because "thunderbolt" sounds much sexier than "HDBaseT " ?

    and with apple, its all about the sexiness, not functionality/practicality.
  • -1 Hide
    JOSHSKORN , June 12, 2012 6:35 AM
    Prediction: We will see Thunderbolt available on SmartPhones. When we do, this port will be able to handle a monitor, external hard drives, speakers and many other USB devices through its Thunderbolt docking station. Obviously a SmartPhone won't need to be attached to a webcam. This will become the future desktop...that is, if it can run Crysis. LOL Had to add that in there. :) 
  • 3 Hide
    pepsimtl , June 12, 2012 7:02 AM
    I remenber scsi interface ,so expensive ,just the company (server) use it .
    and sata interface replace it.
    For me Thunderbolt is the same song
    I predict a sata 4 (12gb) or usb 4 ,soon
  • 13 Hide
    archange , June 12, 2012 7:21 AM
    Hot, expensive active cables cannot be anything else than niche.
  • 7 Hide
    emad_ramlawi , June 12, 2012 7:31 AM
    Technology for the rich ...

    i can wait a couple of minutes for files to be copied on USB 3.0 which is universal and open standard .

    thanks intel but ill pass
  • 4 Hide
    rex86 , June 12, 2012 7:43 AM
    I really hope that this is going to be another flop. USB3 is just fine for almost everything. I do agree that we need open external PCIe standard. We're already paying too much to Intel.
  • 6 Hide
    beetlejuicegr , June 12, 2012 9:46 AM
    Only thing usefull i can see right now is a laptop with intel/amd gpu using it to get access to high end external discrete gpu. All the other possibilities are not needed to be through thunderbolt.
  • -1 Hide
    Anonymous , June 12, 2012 10:15 AM
    What is 125oF in real measurements?
  • 0 Hide
    chesteracorgi , June 12, 2012 12:29 PM
    Thunderbolt is a wonderful innovation and alternative, but hardly ready for prime-time. Even on the Mac platform there is a derth of devices that use thunderbolt. Will thunderbolt be USB or Firewire?
  • -2 Hide
    A Bad Day , June 12, 2012 1:22 PM
    emad_ramlawiTechnology for the rich ...i can wait a couple of minutes for files to be copied on USB 3.0 which is universal and open standard . thanks intel but ill pass


    And if USB 3.0 is too slow, then use two of them (flashdrives in RAID 0 anyone?).
  • 2 Hide
    Anonymous , June 12, 2012 1:38 PM
    I can't believe how narrow some other people comments are. This new standard is for high end users and later others as well once prices start to drop. USB3 eSata when you are working with files that are 10s of Gigs in size are just too slow. Thunderbolt is fast plus easy plug and play for so many future possibilities. There are already a number of hard drives, raids arrays, Displays and now expansion Link PCIe adapter from Mlogic. Already it's potential is becoming interesting.
  • 1 Hide
    josejones , June 12, 2012 2:04 PM
    What are the costs of these new Thunderbolt ports on new z77 motherboards and are they 3rd party?

    I was considering getting the new Gigabyte Z77X-UP5 TH for my new i7 build but, not because of the Thunderbolt ports, but rather, due to the alleged lower mobo temps, which I'm concerned about with our 85F (31C) indoor temps. I await a serious review. These new boards are supposed to be available by the end of June:

    Gigabyte's Hardcore Thunderbolt Demo with GA-Z77X-UP5 TH Motherboard
    http://www.youtube.com/watch?v=deImUH8aUHQ

    Gigabyte Ultra Durable 5 at Computex, shows much lower temperatures
    http://www.youtube.com/watch?v=rLggGetNR14

    z77 Motherboard Discussion
    http://www.tomshardware.com/forum/308058-30-motherboard-discussion
  • 1 Hide
    josejones , June 12, 2012 2:17 PM
    ^ "are they 3rd party?"

    of course not = Intel
  • 1 Hide
    rantoc , June 12, 2012 2:25 PM
    I don't see this tech taking off in the consumer sector any day soon, its to expensive compared to the alternatives and with active cables it ensures that it will remain so! Few have use of the extra bandwidth provided where an usb3 will remain more than sufficient for the masses and the equipment/cables remain cheap!
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