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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  • NCM - Friday, September 23, 2011 - link

    At under a grand for a giant IPS display that incorporates at least $200 worth of extra connectivity (laptop power supply, T'bolt, additional ports, speakers) this monitor is good value for a MacBook Pro or Air user.

    Colour accuracy is more than adequate for most professional work. If it's not good enough you should be taking a big step up to something like an Eizo, both shrinking the display size and doubling the price in the process.
    Reply
  • jecs - Friday, September 23, 2011 - link

    You did read but you just don't understand what color accuracy means or what to do with it.

    What you call poor color accuracy is the gamut space that is important only if you work with wide gamut color. Apple does not cares for wide gamut, not with this display or with past displays. It does not means the display is not accurate in color, it is very accurate. But Apple optimize their displays for print accuracy were wide gamut is not required. Even for FCP Apple doesn't work with wide gamut. For consumer use wide gamut is also a mixed bag because many complain the color in general looks to bright or "artificial".

    I have a 2410 Dell display because I care for wide gamut for what I do but I do appreciate Apple displays and this thunderbolt display is good and other vendors should pay attention to the connectivity and function for desktop use. I would want a mate screen version for more serious professional design but for demanding consumers who appreciate quality and efficiency this is a nice option.

    But right now what you need to know is what display is best for what you do.

    Are you a professional. Are you a consumer or an aficionado looking for an intermediate option. Or buying the cheapest display.

    The Apple displays are for entry level professionals or high end consumers or hobbyist.

    For broadcast professional work or for cheap options look else where.
    Reply
  • hechacker1 - Friday, September 23, 2011 - link

    While I agree with your overall point, I don't think the calibration used by Anand is really informative unless you are doing photo processing work.

    He's targeting the Adobe 1998 profile, which is great for photo editing and printers that support that target (rare unless in a professional setting).

    Most of the Internet is SRGB profile by default, and I'm guessing this display would perform even better there. Most consumer cameras also target SRGB unless you are talking about RAW mode prosumer cameras.

    The fact that this display can accurately display most of the Adobe profile bodes well for its accuracy.

    If you were in Broadcasting or video editing, you should target Rec. 709 profile, which has completely different gamma curves.

    In my opinion, Apple displays are generally very good for the money. Even my late 2009 Macbook Pro can calibrate to excellent color accuracy with VERY little error.

    However, my biggest complaint is that lately Apple displays target 6800-6900K color temps, which are too blue for most calibrations and profiles. Sure it looks good to the untrained eye, but it's bad for color accuracy.
    Reply
  • jecs - Friday, September 23, 2011 - link

    I agree to your more expert opinion than mine.

    Apple is moving more than ever to the high end consumer or prosumer and the move to the higher kelvin could be another sign. Final Cut X and the price is another example.

    But all in all Apple displays are still good monitors.

    If you want a very cheap desktop IPS panel Dell also has a new Ultrasharp line with a shorter gamma space and fewer connectors. But there are other cheap options.
    Reply
  • Ratman6161 - Friday, September 23, 2011 - link

    ...that I would not be in the market for a $1000+ display from Apple, Dell or an other manufacturer. What i'm in the market for is the best I can get for $200 - $300. Now, what I can get for my dell is a docking station that comes with an additional power brick for $129.00. So I can get a decent (not great but decent) 22 to 24 inch display + a docking station well within my budget.

    I guess if a 27" is what you absolutely have to have and you are willing to pay for it, this is a good option...but not for me.
    Reply
  • NCM - Friday, September 23, 2011 - link

    Which is fine and all, but the fact that you aren't in the market for a monitor in this category is completely irrelevant to the discussion.

    What's next, that we start posting about our cats?
    Reply
  • BrooksT - Saturday, September 24, 2011 - link

    Why would you spend $200 on a monitor when you can get a legal pad and pen for $8? I guess if you have to have a computer monitor and you're willing to pay for it, but paper and pen are better options for many people. Reply
  • name99 - Friday, September 23, 2011 - link

    Professionals pay for quality tools.
    Look, if you're earning $100K a year, and this makes you more productive (not to mention happier) it's worth it.

    Are you amazed that professional carpenters don't use $5 saws from Target? That professional truckers rig up the insides of their rigs with fancy electronics? That professional musicians buy high quality instruments, not what they can find on Craigslist?
    Reply
  • seapeople - Friday, September 23, 2011 - link

    You can also buy a $60,000 Cadillac Escalade SUV to pick up your kids at soccer practice.

    What's your point again?
    Reply
  • alphaod - Friday, September 23, 2011 - link

    Nice review as usual; very tempted to purchase one, but I think I'm fine with my current setup; already have a power supply I keep plugged in at times.

    Honestly if Apple added a powerful GPU, yes I think it would a more enticing purchase, but than they'd have the issue of cooling this unit, powering this unit, and constantly upgrade GPUs; at the same time, we'd have people posting online asking all day when the next Thunderbolt GPU updates will come. This would probably also cause problems with pricing; it would come awfully close to the price of an iMac which I'm sure most people would then consider buying an iMac instead (making this product redundant).

    Personally I'd prefer if Apple added an optical drive (for those of us who replaced the optical drives in our MacBook Pro notebooks), optical out, better GPU in the display~Hell forget about releasing this display; redo the iMac as a dock for the MacBook Air/Pro!
    Reply

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