Thunderbolt Performance

The Eagle Ridge Thunderbolt controller is home to two Thunderbolt channels, each one is good for up to 10Gbps in either direction (up or downstream). That works out to be 20Gbps of bandwidth per channel or 40Gbps aggregate between the two. You can only send two channels worth of data down a single Thunderbolt cable, so there's no point to having more than two from a performance standpoint unless you have more than one port on your system.

If DisplayPort and PCIe traffic are indeed carried on separate channels, then the Thunderbolt Display by itself is eating up around 70% of the bandwidth of a single channel on its own (2560 x 1440 x 32bpp x 60Hz with 8b/10b encoding > 6.75Gbps). That leaves 10Gbps in each direction for PCIe traffic. If we look at our benchmarks from the previous section we see that we can hit just under 2Gbps with all of the auxiliary interfaces (GigE, FW800, USB2) running. Given our previous investigation with the Promise Pegasus we know that 8Gbps is feasible there as well. It's possible, that with everything running at once, we could actually run into bottlenecks with Thunderbolt.

To find out I ran a few tests. First I needed a baseline so I threw four SF-2281 SSDs into the Pegasus R6 chassis and configured them in a RAID-0 array. I ran a 2MB sequential read test (QD=16) and measured 909MB/s from the array. This value was obtained without the Thunderbolt Display connected, only the Pegasus R6.

Next I connected the Thunderbolt Display directly to my test MacBook Pro, and then connected the Pegasus to it. I repeated the test, this time getting 900MB/s. Thankfully the presence of the Thunderbolt Display doesn't seem to impact the max data rate I can get from the Pegasus.

For my third test I added a Gigabit Ethernet transfer from a file server to a local SSD using the GigE port on the display. During this test I was also playing back music using the Thunderbolt Display's internal audio codec and speakers. I re-ran the Pegasus test and got 855MB/s.

For my final test I re-ran the third test but added a FireWire 800 to USB 2.0 SSD transfer, both connected to the Thunderbolt Display. I also fired up the FaceTime HD camera on the display using Photo Booth and left it on during the test. The final performance score from the Pegasus was 817MB/s.

Apple Thunderbolt Display Performance

With everything running Thunderbolt performance took a 10% hit. Note that the standard Pegasus configuration isn't able to hit these data rates to begin with, so unless you've pulled out the 12TB of storage and stuck in your own SSDs you won't see any performance drop.

What this does tell me however is the ultra high end users that are looking to daisy chain multiple Thunderbolt storage boxes together may not want to do so. I only have a single Pegasus R6 on hand, but I'm guessing there will be significant performance drop off after the first box. Not that I'm complaining about being able to push nearly 1GB/s over a $49 cable from a notebook, I'm just trying to give a heads up to those who may have aspirations of even higher performance.

Testing the Pieces Display Testing - Color Quality & Uniformity
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  • decryption - Friday, September 23, 2011 - link

    No mention of how the built in Intel graphics perform on the high res screen? It was an initial concern of mine when the new MBA was released - how it would perform at that high resolution when paired up to a Mac running the 3000 HD graphics?

    Any UI lag? (e.g: mission control, swiping full screen apps, etc.)
    Reply
  • boblozano - Friday, September 23, 2011 - link

    Been using this combo for a couple of days and it's just about perfect. No lag, no complaints.

    I'd probably like usb3 and an sd reader as well, but those are nits.
    Reply
  • MonkeyPaw - Friday, September 23, 2011 - link

    I am surprised there's no card reader, but that's amendable by the USB. I don't understand the lack of audio ports. Macs are primarily media machines--how could they forget audio ports?!

    I guess you could use a USB sound card?
    Reply
  • JasperJanssen - Saturday, September 24, 2011 - link

    My guess is, Apple considers the humble analog audio port to be a dodo, except for use while actually on the move. But that's just speculation.

    All of the recent Intel-based macs that have been released, except the MacBook Air (and the Pro, which separates them), have an analog port that doubles as an optical output by plugging in the right (mini-TOSlink) optical cable -- maybe they would only want to include an audio port if it also included that optical part, which may well either make the port too deep for the regular port-location, and/or simply be too expensive. You could put a deeper port on the side of the monitor instead of the rear, but that would be both ugly and pretty expensive, as you'd have to add a whole extra PCB including a cable that goes to it.

    Come to think of it, I'm not sure that at the location of the other port there is enough depth even for a regular 3.5mm jack, let alone a miniTOSlink variant. A 3.5mm jack is about 15-20 mm long and might well simply not fit between the aluminium back and the display backlight.
    Reply
  • TypeS - Friday, September 23, 2011 - link

    I really don't understand why people ponder this. Intel's integrated graphics don't do much for gaming at high resolutions (do AMD and NVIDIA's IGPS either?), but they've been fine for years now for high resolution monitors. Reply
  • Ryan Smith - Friday, September 23, 2011 - link

    If you check the video Anand made for this article, he goes into more detail about MBA performance hooked up to such a large monitor. Overall the performance is respectable, but there are points where the GPU can't keep all of the GUI animations at 30fps. Reply
  • cactusdog - Friday, September 23, 2011 - link

    Its nice to have less cables but this kit would cost around $2500? You can buy a similar res screen+notebook for around half that and take a few extra seconds to plug in a second or third cable.

    For work purposes most people would only really need to plug in the display cable (hdmi/displayport) anyway, and maybe ethernet if theres no wireless...

    I dont think its worth the price premium unless you're getting it for free.....
    Reply
  • TypeS - Friday, September 23, 2011 - link

    Really... half? Dell wants $100 more for their 27" IPS 2560 x 1440 (16:9) display. And doesn;t come close to matching the capabilities of the Thunderbolt display. And a comparable notebook from Acer or Sony aren't much cheaper than the Macbook Air. So.. where are you getting this ultra portable notebook + 27" IPS display all together for only $1250?

    I don't like Apple much taking "facts" out of your arse is just as dumb as Steve Jobs' "magic".
    Reply
  • cactusdog - Friday, September 23, 2011 - link

    What are you talking about? The thunderbolt display is $1200 and the Dell is $899 but with discount you can get it for $750.

    The macbook starts around $1,300 with 13" screen and integrated graphics, then 15' + graphics is $1,699-$2000.

    You can get a similar size/spec Asus or Samsung with discrete for around $900
    Reply
  • cactusdog - Friday, September 23, 2011 - link

    BTW, this is an apple advertisement. People should understand how things work by now and understand how Apple target their marketing. Reply

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