Thunderbolt: Life in the fast lane

When Apple introduced laptops with a new feature called Thunderbolt, many thought that this was a new interface developed by the Cupertino giant, but in truth the technology behind Thunderbolt had been unveiled many years before.

Back in September 2009, while I was covering the Intel Develop Forum, the wraps came off Light Peak – a new interface standard that was set to revolutionise device connectivity. When you’ve been reporting on technology as long as I have, you view launches and announcements with a degree of scepticism, and as always, the proof of the pudding is in the eating, not in the PowerPoint slides.

By early 2011 Intel announced an electrical interface based on the Light Peak specification, called Thunderbolt. The obvious advantage of Thunderbolt was that it could carry 10W of power, allowing external storage devices to function without an independent power supply. The switch from an optical to copper solution also made the standard far cheaper to implement at both ends.

The downside of the Thunderbolt implementation of Light Peak is range. Whereas Light Peak was designed to cater for long distance connectivity, thanks to its optical nature, Thunderbolt is limited by the inherent resistance associated with metal cabling. But this isn’t likely to be much of a problem when it comes to peripheral devices, which are usually placed near the computer they’re attached to.

Shortly after Intel announced Thunderbolt, Apple launched an updated range of MacBook Pro laptops equipped with the new interface. Thunderbolt made use of the already familiar mini-DisplayPort connector that most MacBooks had been equipped with for some time. Of course you could hook your monitor up via the Thunderbolt port, but you could also daisy chain a number of other peripherals, most notably external hard disks.

Thunderbolt has a theoretical maximum data transfer speed of 20Gbps, but of course that bandwidth is shared with everything on the interface, which, more than likely, will include your monitor. Even so, that’s a massive amount of bandwidth, but how does that translate into real world performance?

To help find the answer to the above question, Intel was kind enough to send me a pre-production motherboard – an Extreme Board DZ77RE-75K to be precise – complete with an integrated Thunderbolt controller. As well as the board, Intel sent over a Lacie Little Big Disk external Thunderbolt hard disk enclosure. And just for good measure, Intel removed the mechanical hard disks from the Lacie LBD and replaced them with two Intel 330 SSDs.

To ensure that the Thunderbolt interface would be pushed as hard as possible, I also employed an Intel 520 SSD as the system disk – one of the fastest storage options on the market. And since there were two SSDs in the external enclosure, I also configured them as a striped RAID-0 array for the best possible performance.

As is usually the case with pre-production kit, getting everything up and running wasn’t straightforward, but eventually everything started to play ball and I got Windows 7 installed on the 520 SSD. The next challenge was getting Windows to recognise the Thunderbolt drives. Despite not appearing in the Computer window, firing up Disk Manager showed that Windows had no problem recognising the Thunderbolt interface and the disk enclosure attached to it. Once the two drives were configured under Disk Manager, they appeared with all the other devices under the Computer tab.

To see just how fast the Thunderbolt interface is, I copied a folder filled with four large files totalling 8.39GB from the Intel 520 system disk to the external disk enclosure. The copy was completed in a staggering 34.7-seconds, equating to an average transfer speed of 242MB/sec. I also copied a folder containing 1,048 files, spread across 153 folders and amounting to 22GB of data – this copy took one minute, 29.1-seconds, with an average transfer rate of 247MB/sec!

Copying the same folders from the external enclosure to the system disk took slightly longer – 50.7-seconds and two minutes, 11.1-seconds respectively. This highlights the benefit of the striped disks in the external enclosure, where write speed sees a significant boost. Even so, you’re still looking at average transfer rates of 165MB/sec and 168MB/sec respectively – hardly disappointing when copying from an external drive.

This shows that the real world bandwidth on offer via Thunderbolt is incredible, and even the fastest possible storage components won’t have any problem maxing out over this interface. In essence, an external SSD will be no slower than an internal device connected directly to your SATA bus, which is good news for anyone running low on storage space in their MacBook Air, like me.

The one fly in the ointment is the availability, or lack there of, Thunderbolt peripherals. Since Thunderbolt is considered a Mac interface, peripheral manufacturers have hardly been falling over themselves to jump on the bandwagon. This situation has been exacerbated by the introduction of USB 3.0, which tends to be resident on every new PC or laptop – including Macs.

Unlike with Thunderbolt, there’s no shortage of USB 3.0 devices on the market, but it’s worth remembering that not all USB devices are equal. Unfortunately, most consumers will buy the cheapest USB storage available, either not caring or unaware that these devices will be woefully slow, and offer nowhere near the rated transfer speed.

So, to see how USB 3.0 compared to Thunderbolt I used a 64GB Kingston DataTraveller 3.0. USB 3.0 has a theoretical maximum throughput of 5Gbps, or roughly a quarter of Thunderbolt. Copying the same 8.39GB and 22GB folders from the Intel 520 SSD returned times of one minute, 11.8-seconds and four minutes, 34.5-seconds respectively.

Interestingly, when copying the same folders from the Kingston USB key to the Intel 520 SSD, the times dropped to one minute, one second and two minutes, 23.2-seconds. The reason for this is that the Intel 520 write speed is clearly faster than that of the Kingston USB key. But once again, these results prove that even the fastest devices can’t max out the interface bandwidth.

If Intel’s new motherboard is anything to go by, we’ll soon be seeing Windows-based PCs sporting both Thunderbolt and USB 3.0 connectivity, much like the latest Apple notebooks. This will open up a whole new world of high-speed external peripherals that perform on a par with internal components.

The best part is that even when using lightning fast devices, both these interfaces demonstrate that they have more than enough headroom to avoid any kind of performance bottleneck.

What about the original Light Peak standard? Intel is still developing Light Peak in its optical form, and hopefully I’ll get an update on that progress when I head out to San Francisco for the Intel Developer Forum in September.