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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PWL_Steve - Friday, September 23, 2011 - link
I'm planning on buying an MBA soon so really appreciated the review of the display. For just about the same price, I could purchase the smaller iMac. Would it work the same way with a MBA as the Thunderbolt display would? Buying the IMac would allow my wife to have her own system and I would still be able to occasionally use it as a large display.Thanks
JasperJanssen - Saturday, September 24, 2011 - link
No, the iMac in target display mode *only* provides a display. No power, no USB, no camera, and definitely no ethernet/firewire. I'm not sure about audio -- displayport Target Display Mode included audio as well as video, but the thunderbolt iMac is different enough that I don't know about that one.But as long as the display is all you want, sure, that works. Do keep in mind of course that the smaller iMac is a much smaller (cheaper) display.
tanjo - Friday, September 23, 2011 - link
Apple, the biggest advocate of (almost)everything-in-one. Is it hard to separate the Thunderbolt to the display? If you find the Thunderbolt lacking and need to upgrade, you have to replace the Thunderbolt Display instead of just the Thunderbolt controller - a waste of a perfectly good display. How about making the Thunderbolt "box" dock at the back of the display? It'd still look clean.mcnabney - Friday, September 23, 2011 - link
Like maybe a VESA-compliant box that attaches to the back of any monitor?The lack of logic astounds me.
Oh, no, the iPeople couldn't handle the ugliness of a sleek box attaching to the BACK of their sleek display.
/aren't we in a recession?
slashbinslashbash - Friday, September 23, 2011 - link
No, there's no need to replace the Thunderbolt Display if something better comes out in the future. The beauty of Thunderbolt is that it is chainable, and the Thunderbolt Display has a chainable Thunderbolt jack. You can add an extra box in between the laptop and the Thunderbolt Display, or you can add an extra box after the Thunderbolt Display.Need USB3? I'm sure somebody will come out with a little box with a USB3 controller inside and a Thunderbolt interface. Your use of the Thunderbolt Display does not preclude your additional use of such a USB3 device: just plug it in to the Thunderbolt Display. Need an external GPU? Hook up the MBA to the external GPU Thunderbolt box, and then hook up that box to the Thunderbolt Display. Voila.
You still get 100% use of the stuff built in to the Thunderbolt Display (USB2, GigE, FW800) and you get the additional use of whatever you tack on to the Thunderbolt chain, either before or after the display.
JasperJanssen - Saturday, September 24, 2011 - link
There's not going to be an external GPU that can handle thunderbolt output any time soon. Mini Displayport, yes. Thunderbolt, no. And that means that it'll be a while before you can hook this particular display to an external GPU box, if ever.Everything except external GPU, yes, sure, that's what Thunderbolt is for and will combine great with this display. External GPU: for the time being, will require a VGA/DVI/DP display.
JasperJanssen - Saturday, September 24, 2011 - link
Oh, and I forgot (but there's still no blasted edit button...): Your MagSafe cable will be in the wrong place, if you put a dock between the display and the laptop.Extension cables are available build-to-order at $199 according to google (seems to be they take a complete adapter, and graft a MagSafe laptop port onto it) -- easier just to get a second $99 adapter.
RandomUsername3245 - Friday, September 23, 2011 - link
Since I decided to try using a Mac laptop for work about 6 months ago, and also observing others with Mac laptops, it seems like everyone has a rat's nest of wires running from every port on the computer to various peripherals. I think the lack of a docking station is a big negative for using a Mac laptop in a work environment. This new monitor almost fixes the problem, but unfortunately requires another "Apple Tax" payment.michal1980 - Friday, September 23, 2011 - link
apple obsoletes ports, forces users to buy new products and its called...'Clean Brake'
Microsoft doing something like that and there would be pitch forks.
Phynaz - Friday, September 23, 2011 - link
What computers does Microsoft make?