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
Trouble in Promise-land
What's the first thing you do when you've got a display that has tons of interfaces and bandwidth at its disposal? Try them all at once to see if anything breaks of course. Over the course of the past few days that's exactly what I did. Unfortunately I did find a situation where things broke.
For whatever reason, if you're doing a lot of writes to the Promise Pegasus while playing music (or any other constant audio) through the Thunderbolt Display's internal speakers the audio will eventually corrupt. You can hear exactly what I'm talking about below:
TB Pegasus Audio Issue by AnandTech
This is a recording taken of me listening to music on the Thunderbolt Display (via its internal speakers) while writing a couple hundred gigabytes to the Pegasus R6. Note the introduction of what can only be described as really bad noise at the 6 second marker.
If you stop music playback and quickly resume, the problem will still be there. You have to restart the application that's using the audio codec to recover from this point. From a hardware standpoint, the codec just needs to go through an off/on (sleep/wake?) cycle to return back to normal. If you do this however and haven't stopped the transfer, the problem will creep up again. Stopping the transfer while playing back music won't fix the issue either. You have to stop the transfer and restart the music playback application for it to go away.
The issue goes deeper than that. I went out and bought a Creative Labs X-Fi Go Pro USB sound card to see if the problem stopped at the internal audio codec or extended to all USB sound devices. Unfortunately, it does even happen if you're using an external USB sound card connected to the Thunderbolt Display. Connect the same sound card directly to your Mac or use your Mac's 1/8" stereo jack and the problem goes away.
I was worried that what may appear as noise through speakers could result in data corruption over USB transfers. I ran the Pegasus write test while copying a bunch of files to an SSD attached via USB to the Thunderbolt Display and never saw any corruption on the SSD. This appears to be limited entirely to audio playback.
What's truly bizarre is I can only get the issue to appear when writing to the Pegasus, hundreds of GBs of sequential reads don't seem to produce it. Short bursts of writes don't seem to cause it either. Sending tons of data across the monitor's Gigabit Ethernet, FireWire 800 and USB ports doesn't seem to trigger it either. It appears to be an issue with the Pegasus and the Thunderbolt Display. But which device is ultimately at fault? Is it a problem with the Thunderbolt Display or the Pegasus? Ideally I'd use another Thunderbolt storage device to see if the issue remained, but I couldn't get my hands on a LaCie Little Big Disk.
I thought of something else.
First I needed to test and see if perhaps the issue was related to ultra high speed transfers. As we've already shown, the Pegasus can push as much as 1GB/s over Thunderbolt whereas none of the other bandwidth eaters come even remotely close to that. To determine if the issue was data rate invariant I wrote to the Pegasus at different speeds ranging from 480Mbps all the way up to 7.2Gbps. I tried putting SSDs in the Pegasus as well as standard mechanical hard drives. The problem remained. I got audio corruption regardless of what drives were in the Pegasus or what speed I wrote to the drives. The problem wasn't related to transfer rates.
I also took apart the Thunderbolt Display to confirm there weren't any obvious issues on the controller board (E.g. putting the Thunderbolt IC far too close to the audio controller). Nothing obvious there either.
While I was doing all of this, Apple put forth a Thunderbolt firmware update the other day, however it didn't seem to address the issue either. So I went back to my testing.
Since the problem appeared regardless of how fast (or slow) I was transferring and all I needed was another Thunderbolt storage device to vindicate either the Pegasus or the Thunderbolt Display I turned to the trusty MacBook Air.
As I mentioned in our original Pegasus review, if you have two Thunderbolt equipped Macs and a Thunderbolt cable you can actually put one of the machines in target disk mode and access its drives via Thunderbolt on the remaining Mac. You don't get super high performance but you can get around 500Mbps. Since I had reproduced the audio corruption issue at an even slower data rate I decided to give this a try.
I booted the MacBook Air in target disk mode by holding down the 't' key after turning on the machine. My MacBook Pro was connected to the Apple Thunderbolt Display and a Thunderbolt cable connected the display to the MacBook Air. This was the same setup as the Pegasus, but with the MBA in place of the Pegasus.
I wrote to the MBA just like I did the Pegasus (from a file server connected over the Thunderbolt Display's GigE, transfer rates were capped at around 500Mbps from the file server). After a couple hundred gigabytes were transferred without any audio corruption I swapped out the MBA and connected the Pegasus. I copied the same files at the same rate from the same source. After no more than 7GBs were written to the Pegasus the audio stream started to corrupt.
Based on my testing I can only conclude that the Pegasus seems to be at fault here, not the Thunderbolt Display. Given that the Pegasus was introduced prior to Apple's Thunderbolt Display it's not all that surprising that this issue made it through to production. It's unclear what the root cause is but it's hopefully something Promise can address either through firmware or a driver revision.
Update: I'm still verifying that this is indeed a "fix" but it looks like if you use a USB sound card plugged into a USB hub which is then plugged into the Thunderbolt Display then the sound corruption doesn't happen. This seems to point at noisy power as being the cause with the USB hub acting as a crude filter. It's still not ideal but this may be a workaround for Pegasus users until Promise supplies a fix.
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GotThumbs - Friday, September 23, 2011 - link
Anand,Love the Video Review format. While I think the product is nice and provides access to new tech, I have issues with Apples proprietary format. During a time where many users are going with multi-monitor configurations (I use dual Dell 30" monitors at work). I think combining functionality in a monitor limits/restricts users down the road. I would have liked to see purhaps an external Thunderbolt expansion system that would mount on the back of ANY monitor (via vesa). This would allow users the flexibility to upgrade/swap monitors as needed/desired. In today's technological world, we should be embracing expansion flexibility instead of restriction. It just seems to me that Apple continues to breed products that are proprietary in nature. Reminds me of the old Packard Bell systems where much of the internal hardware was proprietary. Thanks, but no thanks.
Keep up the good work and best wishes.
PS. I've been an AnandTech reader since your HS days.
Constructor - Friday, September 23, 2011 - link
The TBD just adds to the capabilities of your machine, it doesn't take away from it. You can daisy-chain other Thunderbolt add-ons as you want.Nobody prevents anyone from making a multi-port extension box without a display built in. Apple just chose to do it this way. You can even combine both if you want (and once the other announced extension boxes becomne available).
Beyond Thunderbolt being owned by Intel, there's nothing proprietary about the TBD. It's apparently just a relatively straightforward implementation of some of TB's capabilities.
GotThumbs - Saturday, September 24, 2011 - link
Curious, So what other laptops use a MagSafe connector? Other than Apple of course.Whats also curious as Anand pointed out. Why did Apple CHOOSE to leave out USB 3? Next years version will most likely include this. Just seems more of the same tactics used by Apple to keep its consumers re-purchasing much of the same technology to gain one or two new features.
Same with Itouch, Iphone, and Ipad. Same IOS, two items (Itouch and Iphone) are identical for the most part, but one makes calls. The Itouch and Ipad are same but one has bigger screen. Just seems like Apple is more about 'reselling' similar products to the same consumers. How many people purchased an IPAD2 to replace their IPAD, so they could have the camera feature? Apple could have added the camera into the first version but chose not to. Apple has great marketing, but I'm just not wowed by it like many others.
I'll be interested in seeing Thunderbolt added to more PC component products.
Constructor - Sunday, September 25, 2011 - link
The display works exactly the same without connecting the MagSafe connector, but the charging function is indeed limited to MacBooks (iMacs and Mac minis also can't use it).And USB3 in all the PCs with Intel CPUs you see right now is always done by connecting an external USB3 controller to the CPU. In Macs the PCIe lines used for that are instead used to drive the Thunderbolt controller, which is much more valuable. Especially on mobile CPUs with their limited supply of PCIe lanes it would probably not even be possible to drive both.
The next generation of Intel CPUs will provide USB3 directly anyway – and Apple will be able to provide both TB and USB3 at the same time.
To the iPad: I've got an iPad 1 and have not felt any compulsion to replace it with an iPad 2, particularly not for the cameras (the much faster processor and lighter weight would have been a better argument).
Apple keeps updating their product lines, and customers decide for themselves when to buy and when not to. Only relatively few actually jump to the next generation immediately. Most skip one or more generations.
Apple was extremely aggressive in hitting their target price of $499 with the iPad, and they actually made it. Just look at the competition and their difficulties in undercutting Apple there.
It is easy to clamour for them to have included everything and the kitchen sink right away, but that is unrealistic for pricing, development capacity and other reasons.
KoolAidMan1 - Sunday, September 25, 2011 - link
There is nothing proprietary about Thunderbolt. The technology was co-developed by Intel and Apple, and unlike USB the mini-DisplayPort connector has no license fees or usage restrictions associated with it. There is a huge difference between being proprietary and brute forcing a new technology that very few others are using at the moment. This isn't the first time Apple dumped legacy connectors in favor of a new technology.Either way, Thunderbolt will be adopted by more and more PC motherboards and laptops in 2012. There is talk of it being a pretty standard part of Ivy Bridge mobos, crossing fingers.
mlrabbitt - Friday, September 23, 2011 - link
Another +1 for the video review. I would prefer this over the "Conclusion" sections of all your reviews.Conficio - Friday, September 23, 2011 - link
I can' see how I have reduced the cables to my laptop now , but all the extensions are still a dangle of calbes, that even the "cable manage" hardly covers.Why is this not offered in a way where you have bays where storage, or other extensions can be hidden into. Or some sort of back mounting system for this.
In the same vain, where is the rest for the closed laptop on this one or the charging of the wireless keyboard?
I'm also missing some bluetooth for those that want to use wireless headsets.
And the future might just cut the second cord by having an inductive charging matt. Although I guess a laptop needs too much power for that.
Constructor - Friday, September 23, 2011 - link
All Macs already come with Bluetooth. Having another BT interface in the display for the same system would just cause interference without any benefit.And where would the inductive charging mat get its power from, if not through yet another a cable...? ;-)
Shadowmaster625 - Friday, September 23, 2011 - link
What happens when you unplug or lose communication with a pci express card while its interrupt is being serviced? Most likely a blue screen of death. It has always been a source of irritation, but that comes hand in hand with being able to buy low cost products. There is no way to code for every possible fault scenario and also meet any kind of budget.Constructor - Friday, September 23, 2011 - link
Thunderbolt-capable drivers will certainly need to survive device disconnection without blowing up the kernel. But beyond that, there should be little need for modification, if any.