The Apple Thunderbolt Display Review
by Anand Lal Shimpi on September 23, 2011 2:56 AM EST- Posted in
- Displays
- Mac
- Apple
- Thunderbolt
- Thunderbolt Display
Multi-monitor with the Thunderbolt Display
The Thunderbolt Display has a single Thunderbolt port for daisy chaining additional devices. Each Thunderbolt port can support 7 additional devices, which means 6 devices once you connect the Thunderbolt Display. These devices can be anything Thunderbolt, however you cannot connect a DisplayPort monitor to the Thunderbolt Display directly. If you want to connect another monitor directly to the Thunderbolt Display it must be another Thunderbolt Display. To understand why, we need to look at the architecture of a Thunderbolt controller.
This is the first Thunderbolt controller Intel introduced, codenamed Light Ridge:
You see it has four Thunderbolt channels and two DisplayPort inputs. It also has a single DisplayPort output as well as a DisplayPort passthrough option. What's the difference? If there are only two devices in the chain, the computer and a DisplayPort monitor, you can use the DisplayPort passthrough option bypassing the majority of the logic entirely. This is how the 2011 MacBook Pro can connect directly to a DisplayPort display. Put a Thunderbolt device in between those two devices and you can no longer use the passthrough mode. You have to send a Thunderbolt signal to the Thunderbolt device, and it can then extract the DisplayPort signal and output it. Simply passing DisplayPort through won't work.
I originally believed Apple used the smaller Eagle Ridge controller in its Thunderbolt Display, but now believe that to be incorrect. Upon closer examination of our dissection photos it appears that the 27-inch panel is driven by an embedded DisplayPort (eDP) connection. If I'm right, that would mean the DisplayPort output from the Light Ridge controller is routed to the eDP connector in the display. With its sole DP output occupied by the internal panel, the Thunderbolt Display cannot generate any more DP signals for anything connected directly to its Thunderbolt Port.
If you connect a Mac to the Thunderbolt Display what is sent is a Thunderbolt signal. DisplayPort is broken off and sent to the display but there's no way to propagate an additional DisplayPort signal to any other non-TB displays in the chain. The output on the Thunderbolt Display is literally a Thunderbolt output, it can't double as DisplayPort.
However, if you connect another Thunderbolt device that uses Light Ridge you can split any additional DisplayPort signals out of the chain. In other words, if you connect the Thunderbolt Display to a Promise Pegasus you can then chain on another DP panel. If you own a 27-inch Cinema Display and were hoping to add the Thunderbolt Display to it on the same Thunderbolt chain, you will need another TB device in between.
There are also the obvious GPU limitations. The 13-inch MacBook Pro only supports two displays (Ivy Bridge will up this to three). If you manage to connect two to the 13 however, Apple will just blank the display on the notebook and drive the two external panels. The MacBook Air is a different story. Not only does it only support two displays, but the Eagle Ridge controller only has a single DisplayPort input so you're not driving more than one external display via a MBA no matter what you do.
I tested multimonitor functionality with a 27-inch LED Cinema Display as well as a second Thunderbolt Display. In the case of the Cinema Display, as expected, I couldn't get video out of the port on the Thunderbolt Display. Connecting the Thunderbolt Display to a Promise Pegasus and then connecting a Cinema Display to it worked however. I also woke up the MacBook Pro's internal display and confirmed that I could get all three functioning simultaneously. There's a definite slowdown in UI frame rate with two 27-inch panels being driven by the MacBook Pro's integrated Radeon HD 6750M. It's not unbearably slow but kiss any dreams of 30 fps goodbye.
I also confirmed that two Thunderbolt Displays worked on the MacBook Pro regardless of the connection configuration.
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name99 - Friday, September 23, 2011 - link
"The iMac and displays like this compell people to discard those expensive displays far ahead of their time and likely buy another display of the same size and resolution."And discard means WHAT? I can go to eBay and see the prices for second hand macs. What's stopping you from selling your iMac, or giving it to a friend/family member/school?
You claim there area significant number of still-working flat-screen iMacs in closets or the trash. I call bullshit.
dave1_nyc - Friday, September 23, 2011 - link
Anand, I liked the review, and I think this sounds like interesting technology, but honestly, but you sound as though you've never used a docking station. Yes, you're right, they are all proprietary, but the good ones from Dell and Toshiba (and I'm sure others) are terrifically useful if one needs one.I don't, but there are people in my org for whom their laptops are their main machines and they take them back and forth between the office and home every day. All the modern docking stations provide pretty much any connectivity you could want, and they allow you to use any monitor you want, and switch out monitors.
Further, while connecting two cables (a la the review) isn't hard, with the laptops and docking stations we have you walk up and set the laptop down onto the station connectors. At which time the laptop (if thus setup) turns on, adjusts for the external display (or two), and that's that. If you have automatic login, you never have to open the laptop.
Expensive? We pay $150 for them, and with that comes the freedom to upgrade either the docking station (such as when the USB 3 ones come out early next year) or the monitor independently of each other.
Of course, the real docking stations (as opposed to those USB 2 things) are only found in 'business class' machines, but those machine can now be configured with discrete graphics if one wants.
I'm not trying to sell docking stations, but you're usually not quite so inaccurately dismissive.
jecs - Friday, September 23, 2011 - link
I agree with you. I think Apple or someone else should produce a docking station for Mac Books. I remember when I used those with an IBM laptop some years ago.If you want to use "an all Apple technology" the thunderbolt display is fine. But if you want a MBP and have a different need you will find yourself limited in options. But those parts need to be competitive in price and quality.
Constructor - Friday, September 23, 2011 - link
Why are you limited? Simply use a different Thunderbolt docking solution instead of the ready-made Thunderbolt Display.With Thunderbolt you can even customize your own special solution in a way you never could before, by daisy-chaining multiple Thunderbolt devices according to your own specific needs.
And the kicker is that you can carry it all over to a new machine, even when switching manufacturers and even platforms!
None of the pre-existing docking solutions ever came close to that.
Trefugl - Saturday, September 24, 2011 - link
But where are all these external devices that I can so easily purchase and make my own docking solution? Last I checked (admittedly a few weeks ago), there was a very limited selection on adapter types on the market.I do agree that this is a great solution (and one that actually makes me excited about thunderbolt), the problem is that no one has made an external hub like what's in the display yet... they might now that PCs are getting the same connector next year, but it just blows my mind that the first place you see this tech is stuffed inside a monitor (one that only can work at all with new '11 Macbooks...)
Constructor - Saturday, September 24, 2011 - link
Well, it works with all current Macs (the Mac Pro is the only one that hasn't been upgraded to Thunderbolt yet).And I would not be surprised if the availability of Intel Thunderbolt controllers was one of the reasons why third party devices are being delayed – at the number of Macs Apple is producing, it is quite possible they're buying every chip Intel manages to get out the door. But Intel has lots of experience with mass production of high-grade chips, so I have no doubt availability will catch up soon if it hasn't already.
Belkin is apparently designing effectively a Thunderbolt Display without the display:
http://gizmodo.com/5839952/belkins-thunderbolt-exp...">Belkin's Thunderbolt Express Dock Finally Gives You a Reason to Remember You Have Thunderbolt
And there's more in the pipeline from various manufacturers. Unsurprisingly, professional-grade interfaces which actually need the speed and low latency are among the first.
Constructor - Saturday, September 24, 2011 - link
The link has been crippled, apparently. This should work:http://gizmodo.com/5839952/belkins-thunderbolt-exp...
AbRASiON - Friday, September 23, 2011 - link
Defective by design.stepa - Friday, September 23, 2011 - link
Simple question (requires a simple answer)So does it mean that there is no way to connect this display to a windows pc as a main display?i know that with previous models you could use an adapter or newer gfx cards already have a display port.so this a no go for pc users?
KPOM - Friday, September 23, 2011 - link
Not until PCs with Thunderbolt ports start coming out next year. I suspect a lot of the Ultrabooks will do so since Thunderbolt support will be built into some of the Ivy Bridge chipsets.