Everything You Need To Know About Thunderbolt

Thunderbolt Controllers: Five Flavors, All Intel

Five Flavors, All Intel

Systems supporting Thunderbolt technology are not all created equal. Although Intel currently holds a monopoly on Thunderbolt-capable controllers, the tech is actually available in several flavors.

Controller Code Name
Model Number
Thunderbolt Channels
PCIe Interface
Package Size
Cactus Ridge 4C
2 outputsx4 Gen212 x 12 mm2.8 WPC, Daisy-chainable devices
Cactus Ridge 2CDSL33102
1 outputx4 Gen212 x 12 mm2.1 WPCs
Port Ridge
N/Ax2 Gen26 x 5 mm0.7 W Endpoint devices
Light Ridge
2 outputsx4 Gen215 x 15 mm3.2 WPC, Daisy-chainable devices
Eagle Ridge
1 outputx4 Gen28 x 9 mm1.8 W PCs, Endpoint devices
Notes: Bold indicates Second-gen controller

When Apple originally launched its Sandy Bridge-based Macs, many of them supported Thunderbolt using Intel's Eagle Ridge controller, which enables a single Thunderbolt port, support for one DisplayPort device, and a four-lane PCI Express 2.0 interface to the host platform. If you want to start daisy chaining peripherals, however, you need the more expensive Light Ridge controller, which offers two Thunderbolt ports.

But Intel is not sitting idle. With the introduction of its Ivy Bridge-based platforms, Intel’s partners plan to use a second-generation Thunderbolt controller family referred to as Cactus Ridge that comes in two- and four-channel variants. Because a single port requires two channels, the higher-end 4C model supports two ports, while the 2C SKU enables one Thunderbolt port.

According to Intel's partners, Ultrabooks will employ the single-port Cactus Ridge controller due to its lower power consumption. Enthusiast-oriented desktop systems and daisy-chainable devices will employ the Cactus Ridge 4C for its dual-port support. Both Cactus Ridge parts utilize a four-lane PCIe 2.0 interface. It was previously thought that the 2C version would monopolize two lanes, but we've confirmed that those reports were mistaken.

Intel’s Port Ridge controller is also a second-gen development. However, it's specifically designed to enable Thunderbolt-based endpoints. Devices employing the Port Ridge controller have to be set at the end of your daisy chain (if there is one) or used individually. Elgato’s Thunderbolt-based SSD, a portable 2.5” external SSD with a single Thunderbolt port, is a good example of an endpoint device. And because Thunderbolt delivers up to 10 W of power, you won't have to worry about a separate power cable for products like this one.

Why all of the differentiation in Thunderbolt controllers? Intel is trying to make the technology more affordable where it can. We hear that Light Ridge costs somewhere between $25-$30, and Eagle Ridge supposedly runs around half of that. Port Ridge is, in effect, half of an Eagle Ridge controller, removing Thunderbolt channel used for DisplayPort signaling. Thus, as a single port single channel controller, Port Ridge allows vendors to partially mitigate the expense of enabling Thunderbolt on their end-point devices.

Dual Display Support

The Cactus Ridge 4C and Light Ridge controllers both featuring dual DisplayPort outputs. On the desktop, one pipeline comes from the Sandy or Ivy Bridge-based HD Graphics engine. The other requires interaction with an add-in graphics card. Of course, the option to attach a second screen is important on high-end systems, which is why enthusiast-class Z77 motherboards will feature the four-channel Cactus Ridge controller. Implementation-wise, that's going to look a little strange because you need a DisplayPort loop-back cable between discrete graphics and the motherboard itself. But it's the only way to establish a second path to the Cactus Ridge 4C controller. 

"Why not just hook your monitor up to the graphics card, and forget about all of that hassle," you ask? Remember: Thunderbolt uses an active cable.

An active cable allows Thunderbolt to communicate with displays physically farther away without compromising signal integrity. A long DisplayPort cable isn't necessarily a good option because the signal degrades after two meters. DVI uses only passive cables, causing resolution and refresh rate reductions as length increases (that's why DVI boosters exist). Thunderbolt solves those problems and simplifies display connectivity.

Thunderbolt-Supported Macs
TB Controller
Thunderbolt Ports
Integrated Graphics
Discrete Graphics
Max # Of Connected Displays
MacBook Air (Mid 2011)
Eagle Ridge
MacBook Pro (13-inch, Early 2011)
Light Ridge
Mac mini (Mid 2011) 2.3 GHz
Eagle Ridge
Mac mini Lion Server (Mid 2011)
Eagle Ridge
MacBook Pro (15- and 17-inch, Early 2011)
Light Ridge
iMac (Mid 2011)
Light Ridge
Mac mini (Mid 2011), 2.5 GHz
Light Ridge

Providing that a mobile system with Thunderbolt includes the Light Ridge or Cactus Ridge 4C controller, you can enable dual-monitor output using only integrated graphics. The 13.3" MacBook Pro serves as a good example.

All MacBook Pros feature the Light Ridge controller. On the 15" and 17" MBPs, specifically, Apple does routes a second DisplayPort signal from discrete graphics to the on-board Thunderbolt controller. Yet, the 13.3" model only comes with Intel's HD Graphics 3000. In the case of the smaller MacBook, Apple routes both DisplayPort signals from the integrated graphics subsystem to the Light Ridge controller. The catch is that HD Graphics 3000 only supports two displays. And that's why the 13.3" panel goes blank if you plug in a second 27" Thunderbolt Display.

Ivy Bridge's HD Graphics 4000 engine offers up to three independent displays. So, configurations lacking add-in graphics, but equipped with Light Ridge/Cactus Ridge 4C, still have the potential to drive two Thunderbolt screens without sacrificing the notebook's display.

If your notebook has a Eagle Ridge or Cactus Ridge 2C controller, you can only drive one Thunderbolt display. This is a limitation of the controller, so even if you have discrete graphics, a second Thunderbolt-equipped device cannot be attached.

Technically, it is possible to drive two displays via Thunderbolt using Intel's integrated graphics subsystem on a desktop, but the machine has to meet several requirements for this to happen.

  • The motherboard must have a Light Ridge or Cactus Ridge 4C controller.
  • Your motherboard must have a DisplayPort input port to route the second display signal.
  • You motherboard must have a built-in DisplayPort output port (from Intel HD Graphics 3000/4000), which is looped back to the input port.

Even though it's more work to hook up a loop-back cable, there's a legit reason for its existence. The cable gives you the option to drive a second screen using discrete graphics. Without that, you'd have no way to run a Thunderbolt monitor from a high-performance graphics card.

This thread is closed for comments
    Your comment
  • Pyree
    I was really hoping to see some eGPU benchmark. Oh well, I guess I have to wait.
  • mayankleoboy1
    thunderbolt will fail after external PCIE standard is implemented
  • mayankleoboy1
    for more insight of thunderbolt fail and Intel's lying :

  • shoelessinsight
    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.
  • A Bad Day
    Looks like I'm going to steer clear of Copperpeak for my future build.
    Cost is going to kill this.
  • mayankleoboy1
    because "thunderbolt" sounds much sexier than "HDBaseT " ?

    and with apple, its all about the sexiness, not functionality/practicality.
    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. :)
  • pepsimtl
    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
  • archange
    Hot, expensive active cables cannot be anything else than niche.
  • emad_ramlawi
    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
  • rex86
    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.
  • beetlejuicegr
    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.
  • What is 125oF in real measurements?
  • chesteracorgi
    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?
  • A Bad Day
    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?).
  • 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.
  • josejones
    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

    Gigabyte Ultra Durable 5 at Computex, shows much lower temperatures

    z77 Motherboard Discussion
  • josejones
    ^ "are they 3rd party?"

    of course not = Intel
  • rantoc
    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!
  • josejones
    Will the new ipad, iphone etc have a Thunderbolt port?
  • bigjuliefromchicago
    Considering that the number of peripherals available is approximately zero, I'd say this theoretically great technology is practically useless.
  • xenol
    Thunderbolt has all the signs of FireWire: it's faster and can provide power. It also has the added effect of "we already having something universal".
  • jimmysmitty
    rex86I 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.

    Yea because paying $220 for a 2500K is too much.....

    Honestly its suprising to me to see people talk like this. Technology has to move forward. USB 3.0 is fine for some applications but the interface was not designed for high bandwidth operations such as flash drives/eHDDs. It chokes thanks to the 8b/10b encoding that causes a large drop in thoroghput.

    And people act as if USB 3.0 was as cheap as USB 2.0 to start and it wasn't. Everything new starts at a higher price and drops when it becomes more widley used.

    Thunderbolt has a lot of potential to increase external devices capabilities. I don't see myself ever using it but it will probably be used in places that need that kind of speed and when it hits 50Gbps via optical I am sure those same people will love it.