Thunderbolt: II FireWire, Fibre Channel VIII or ePCIe or II? - I

It is now over a year since the first MacBook Pro with a port Thunderbolt arrived on the market. The supply compatible hardware remains weak, the PC barely gets started, and frustration for Mac users, private property Thunderbolt (rare and too expensive) or USB 3 is felt on the forums. The imminent release of the first Mac Ivy Bridge is an opportunity to take stock of the particular position of this interface.


Contrary to what has been read, Thunderbolt is not an evolution of Light Peak: this is simply a new name. It is far from the first prototype, based on fiber optics and USB connectors, but nothing has fundamentally changed. The Thunderbolt is a combination of two technologies: PCI Express for the data and DisplayPort for display. The two signals are multiplexed at the source and demultiplexed by the unit target. A surprise, that the Thunderbolt has finally adopted the Mini DisplayPort. Without it’s in its first version, appeared in late 2008 with the first MacBook Pro Unibody, yet he was quickly adopted by the association as VESA DisplayPort connector for the AC. He then went multi-channel audio that is the interest of the original interface, in addition to its compatibility with high definition.

DVI and HDMI its close cousin could not go much further than the definitions HD. A limitation that account, when the Retina screens appear imminent. Quickly finalized, the Mini DisplayPort interface is quietly becoming the best endowed in his generation rate (17 Gb / s in version 1.2). Thunderbolt devices are of course compatible with the Mini DisplayPort hardware, but with restrictions: one Mini DisplayPort display by making Thunderbolt, or directly connected to the Mac end of the chain, through any device other than a screen Thunderbolt .

On the Mac Pro 2007, the expansion slot utility is launched automatically when to arbitrate the bandwidth between the PCI Express. The operation is then automated.

A major interest of combining technologies PCI Express and DisplayPort is the virtual absence of any driver: most platforms already recognize them. The trick is to see these elements to the system as if they were locally connected and totally ignore the Thunderbolt connectors. Thus began the legitimate debate on the survival of the Mac Pro, now that the way is open for external PCI Express cards.

Before the Thunderbolt, PCI Express external systems such as Magma ExpressBox1 were necessary to add additional cards to a desktop or a laptop.

The debate may seem new, but the audiovisual industry, a market most interested in the Thunderbolt, has extensive experience in outsourcing expansion cards. Whether it's rude beginnings of external PCI chassis or PCIe interfaces latest. The latter are connected directly to the PCI Express bus via internal expansion card standard, or an ExpressCard for laptops.

The card input-output external HD with Avid Mojo DX connects PCI Express External, via a PCIe ExpressCard or specific. The first Mojo, limited to standard definition video (SD), was connected by FireWire.

Technical, but transparent

Several patterns (or "topologies") are possible when designing an interface. Those that we use are the star topologies (USB) or tree (FireWire). The latter, more versatile, has been selected for the Thunderbolt, which does not prevent the use of hubs (or "hubs"). To chain up to 7 devices (including computer), the stress is minimal: the screens must be pushed to the end of the chain, especially in the case of an iMac used as a monitor ("Target Display Mode"). We saw this configuration on Mac with SCSI and FireWire (8 and 63 units, respectively). And like them, the Thunderbolt can turn a Mac into a single external drive through the target mode ("Target Mode").

Through hubs and converters expected to be more flexible, the Thunderbolt is the missing link in the middle of disparate interfaces. If its assets to a desktop machine are obvious, they are more for a laptop: for mobile use, the machine continues to separate itself from anything that might encumber its weight and battery life (the optical drive is the next likely target). And sedentary mode, it has a universal connector, suitable for transforming a gesture very powerful workstation. The best example for the shot does not come from Apple, but Sony, with a customized version of the Thunderbolt, designed a promising docking station for its VAIO Z. The technology is recent, all is not smooth. In return, the rate of development since the first evocations of Light Peak has something left speechless. Dysfunctions affecting some devices should be settled between the manufacturer and Intel, and some limitations of Windows Thunderbolt (or sleep or warm start) will last only time a further incorporation in Windows 7. For the record, the development of FireWire had experienced a few setbacks, long forgotten in favor of the qualities of the interface.