One by one the barriers to mobile computing have been falling. In the early days you could move to a notebook but you'd give up a lot of CPU, GPU and I/O performance. SSDs really fixed the storage performance issue (2.5" hard drives are horrendously slow compared to their 3.5" counterparts), power gating and turbo boost helped address the CPU problem and I wouldn't be too surprised to see companies have another go at external GPU solutions for those who need the added graphics horsepower.

The idea of external GPUs brings up the current limitation we face in this mobile transition. Although being more mobile is great, we still want the best of both worlds: great performance when we're at a desk, and great battery life when mobile. Enabling the former is going to require new technologies as well as new high speed interfaces.

Intel has been at the forefront of many of the successful high bandwidth interfaces in the evolution of the PC industry. Will Thunderbolt be another feather in its cap? In February we got the first Thunderbolt enabled MacBook Pros and just last week Promise shipped the first Thunderbolt enabled storage device. It's time to put the two together.

Thunderbolt Recap

At the beginning of this year Intel, alongside Apple, finally introduced a productized version of the interface we'd previously only known as Light Peak. Given that the first instantiation of this interface used traditional copper wires and not an optical interface, Apple and Intel branded it Thunderbolt.

Thunderbolt Controller IC on 15" 2011 MacBook Pro - Courtesy iFixit 

The interface is royalty free, although Intel is the only company that makes Thunderbolt controller needed to support the interface. There's no word on the cost of the Thunderbolt controller. Thunderbolt isn't an Apple exclusive, however we won't see PCs ship with the high bandwidth copper interface until 2012 at the earliest.

Thunderbolt is a high speed, dual-channel serial interface. Each channel is good for up to 10Gbps of bi-directional bandwidth (20Gbps total) and with two channels a single Thunderbolt link is enough for 40Gbps of aggregate bandwidth.

Thunderbolt can carry both PCIe and DisplayPort signaling. Apple claims that one of the channels is used for DisplayPort while the other is used for PCIe. DisplayPort interface support extends to the connector, which is physically compatible with a standard mini-DisplayPort connector. DisplayPort support is key as it allows video to be carried in addition to data, potentially allowing for some interesting use as a single cable docking solution for notebooks.

In addition to carrying up to 40Gbps of total bandwidth, a single Thunderbolt cable can also deliver up to 10W of power to connected devices.

Each Thunderbolt port can drive up to 7 daisy chained devices, although all devices must share the 40Gbps (up/down) bandwidth to the host.

There's an obvious comparison to USB 3.0 which currently tops out at 5Gbps, however even it offers only 1/4 of the total available bandwidth of the Thunderbolt PCIe channel (not to mention its inability to carry DisplayPort).

The Pegasus: Hardware
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  • Exodite - Friday, July 8, 2011 - link

    Point being, they have no reason to do so.

    What possible use is Thunderbolt to consumers?

    Had LP been piggybacked upon USB instead it would have allowed for both back- and forwards-compatibility with a huge market of devices and could have slowly permeated said market until it had become a de-facto standard.

    The choice of using mini-DP may well have condemned it to being yet another Firewire.
  • Exodite - Friday, July 8, 2011 - link

    Mini-DP isn't vastly superior to any other display interface.

    The differences between DP 1.2 and HDMI 1.4a are at best a trade-off, with the latter being the better choice for consumers - even disregarding the huge difference in market penetration.

    Computers currently shipping with mini-DP - Apple Macs and those equipped with discrete AMD 5- and 6-series graphics cards.

    Unfortunately that's not the main issue, which is the distinct lack of /displays/ using the standard.

    Displays shipping with mini-DP - Apple Cinema displays. The end. A few other high-end professional displays ship with full-sized DP but you can't argue it's got any significant market penetration.

    Then there's HDMI, which is pretty much ubiquitous in the consumer electronics world, seeing rapid adoption for computer displays and is also used in modern projectors.

    Anyway, that's pretty much an aside - the real gist of it is what I already mentioned regarding USB/LP being the vastly superior choice.

    As for USB connectors only being allowed to be USB connector, that's not a physical limitation - it's a matter of licensing and what they choose to name the standard. A theoretical USB/LP standard could just as well have been named 'USB 4.0' or whatever.
  • Focher - Saturday, July 9, 2011 - link

    Not sure what your point is here. Is it just about the connector type? USB and Thunderbolt are different technologies. TB needed a display standard. DP was chosen because 1) Apple participated in its creation and 2) it isn't saddled with the restrictions and costs that HDMI licensing does.
  • repoman27 - Sunday, July 10, 2011 - link

    Mini DisplayPort IS DisplayPort, just using a smaller connector. The size of the connector is irrelevant to the interoperability of the devices, you simply connect them using an appropriate cable.

    A quick search of Newegg shows displays available from Asus, BenQ, Compaq, Dell, HP, Lenovo, NEC, and Samsung all with DisplayPort connectors.

    ATI/AMD has been shipping cards with DisplayPort connections since early 2008, and DP is native to the GPUs used for every 5 and 6 series device. Intel began including DisplayPort capability with GMA 4500 in 2008 and currently ships it to you in every CPU with integrated HD graphics. NVIDIA is the only major player who seems to be lagging on DP adoption, but there are still plenty of Fermi based cards on the market rocking DisplayPort.

    HDMI was developed for consumer electronics, i.e. televisions and home theaters. DisplayPort was developed for PCs. The lineage is distinct and continues to this day as the two evolve. DP is packet based so that multiple displays can be daisy chained off of one port, which is not a common usage model for TVs. Newer HDMI specs include such home theater relevant features as support for 3D formats, 100 Mbps Ethernet and an audio return path—something that makes no goddamned sense in the PC context. DP originally supported high-resolution displays but not audio, whereas HDMI included audio from the outset but could only drive a 1920x1080 display because that’s all that HDTV required. DP 1.2 has an AUX channel that can be used to provide a USB 2.0 connection to the display over the same cable as video and audio, as well as offering more than twice the total bandwidth of HDMI 1.4.

    USB is a shared serial bus based on a tiered-star topology. It’s great for connecting lots of relatively slow devices that don’t require much bus power or tight timing. When you try to use it for devices that require lots of bandwidth, like high speed external storage, things go downhill fast. Even with a single device connected to a USB host controller, you’re lucky to get throughput equal to 60% of the oft touted “480 Mbps” or “5 Gbps” due to insanely high protocol overhead. Although it’s finally moved beyond half-duplex and added better support for bulk data transfers, the cluster that is USB 3.0 tops out at around 385 MBps in best case scenarios. To create backwards compatibility with 2.0, they merely created Siamese Frankenconnectors, doubling the dimensions of the B connectors in the process, and added more conductors to the cable. How would bastardizing this poor port any further be a good idea? The differences between Thunderbolt and USB in architecture, implementation, and intended use are vast. How would the average user make this distinction if they were somehow cobbled onto the same port?
  • taltamir - Friday, July 8, 2011 - link

    it doesn't have such potential, because it is an active cable that costs 50$ per cable.
    Daisychaining doesn't help reduce the amount of CABLES you need, you still need one cable per device. It just reduces the amount of ports you need.

    So I will stick with my 5 cables for 2$ each instead of 5 cables for 50$ each.

    Now, if they made a thunderbold cable that is passive and cheap as hell, and integrated the controller into southbridge, then it will have the potential to replace all other cables.

    Not having royalties and being an extension of PCIe are very powerful features as you said yourself.
  • HW_mee - Friday, July 8, 2011 - link

    I though the unofficial Apple slogan was "It just works", but after reading the description for using an Imac as secondary display, that slogan seems like a joke. You have to boot up the Imac, own a recent keyboard and press a slightly odd key combination, that does not fit my impression of something that "just works".
    You use the Imac as a screen and Displayport is part of the cable, why could they not just have a on/off switch for the screen and one for the complete Imac, the screen switch can only control the screen and the Imac switch starts screen and computer, if the Imac is on, the screen switch is deactivated, not exactly advanced science.

    Reading the review I also got the impression that Apple have given up on security, is there no password protection or something similar in "Target disc mode"? Can you just buy a Thunderbolt cable for a new Macbook pro and start stealing data from other Thunderbolt equipped Apple computers, just by connecting the cable and holding down t when the "victim" is started?
  • HW_mee - Friday, July 8, 2011 - link

    Replying to myself :-/

    Target disk mode is seriously a horrible feature, from a security view, it even works with FireWire and I can not find any references to any security.

    Remember kids, a login password protects you data, unless the bad guy remembers a 4$ cable.
  • xype - Friday, July 8, 2011 - link

    Uhm, as soon as someone has physical access to your computer (which Target Disk Mode implies), short of encrypting your whole disk (with, say, or any other encrypting software), you can kiss your data goodbye.

    Also, how’s Target Disk Mode any different than an USB key? If anything, the latter is easier to deal with, since you can just plug it into a running machine and off you go. Target Disk Mode might annoy you with stupid things like a Login and whatnot.
  • Penti - Friday, July 8, 2011 - link

    Physical access is physical access. Just set up a EFI/BIOS password if you want false security. If your concerned about your noisy friend with another mac and firewire/thunderbolt-cable. Or whatever. If you like to protect your data, then encryption is not really enough either, but it helps. It does protect against someone stealing your shut down computer. If you have it on, they encryption key is in memory however. When you have physical access it doesn't really matter what the firmware tries to do, passwords and lojack can all be circumvented, and of course you could just remove the drive from the computer when it's not encrypted any way. Computers don't have protection from and are never protect from physical access. You need physical security for that.
  • HW_mee - Friday, July 8, 2011 - link

    It is one thing if the thief steals the HDD/computer, learns a password or hacks the computer using some piece of software, as this often takes time, requires a lucky break or leaves obvious traces.
    Another thing is if someone can just hook up a cable turn the computer on and press T to access everything.

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