Driving the Retina Display: A Performance Discussion

As I mentioned earlier, there are quality implications of choosing the higher-than-best resolution options in OS X. At 1680 x 1050 and 1920 x 1200 the screen is drawn with 4x the number of pixels, elements are scaled appropriately, and the result is downscaled to 2880 x 1800. The quality impact is negligible however, especially if you actually need the added real estate. As you’d expect, there is also a performance penalty.

At the default setting, either Intel’s HD 4000 or NVIDIA’s GeForce GT 650M already have to render and display far more pixels than either GPU was ever intended to. At the 1680 and 1920 settings however the GPUs are doing more work than even their high-end desktop counterparts are used to. In writing this article it finally dawned on me exactly what has been happening at Intel over the past few years.

Steve Jobs set a path to bringing high resolution displays to all of Apple’s products, likely beginning several years ago. There was a period of time when Apple kept hiring ex-ATI/AMD Graphics CTOs, first Bob Drebin and then Raja Koduri (although less public, Apple also hired chief CPU architects from AMD and ARM among other companies - but that’s another story for another time). You typically hire smart GPU guys if you’re building a GPU, the alternative is to hire them if you need to be able to work with existing GPU vendors to deliver the performance necessary to fulfill your dreams of GPU dominance.

In 2007 Intel promised to deliver a 10x improvement in integrated graphics performance by 2010:

In 2009 Apple hired Drebin and Koduri.

In 2010 Intel announced that the curve had shifted. Instead of 10x by 2010 the number was now 25x. Intel’s ramp was accelerated, and it stopped providing updates on just how aggressive it would be in the future. Paul Otellini’s keynote from IDF 2010 gave us all a hint of what’s to come (emphasis mine):

But there has been a fundamental shift since 2007. Great graphics performance is required, but it isn't sufficient anymore. If you look at what users are demanding, they are demanding an increasingly good experience, robust experience, across the spectrum of visual computing. Users care about everything they see on the screen, not just 3D graphics. And so delivering a great visual experience requires media performance of all types: in games, in video playback, in video transcoding, in media editing, in 3D graphics, and in display. And Intel is committed to delivering leadership platforms in visual computing, not just in PCs, but across the continuum.

Otellini’s keynote would set the tone for the next few years of Intel’s evolution as a company. Even after this keynote Intel made a lot of adjustments to its roadmap, heavily influenced by Apple. Mobile SoCs got more aggressive on the graphics front as did their desktop/notebook counterparts.

At each IDF I kept hearing about how Apple was the biggest motivator behind Intel’s move into the GPU space, but I never really understood the connection until now. The driving factor wasn’t just the demands of current applications, but rather a dramatic increase in display resolution across the lineup. It’s why Apple has been at the forefront of GPU adoption in its iDevices, and it’s why Apple has been pushing Intel so very hard on the integrated graphics revolution. If there’s any one OEM we can thank for having a significant impact on Intel’s roadmap, it’s Apple. And it’s just getting started.

Sandy Bridge and Ivy Bridge were both good steps for Intel, but Haswell and Broadwell are the designs that Apple truly wanted. As fond as Apple has been of using discrete GPUs in notebooks, it would rather get rid of them if at all possible. For many SKUs Apple has already done so. Haswell and Broadwell will allow Apple to bring integration to even some of the Pro-level notebooks.

To be quite honest, the hardware in the rMBP isn’t enough to deliver a consistently smooth experience across all applications. At 2880 x 1800 most interactions are smooth but things like zooming windows or scrolling on certain web pages is clearly sub-30fps. At the higher scaled resolutions, since the GPU has to render as much as 9.2MP, even UI performance can be sluggish. There’s simply nothing that can be done at this point - Apple is pushing the limits of the hardware we have available today, far beyond what any other OEM has done. Future iterations of the Retina Display MacBook Pro will have faster hardware with embedded DRAM that will help mitigate this problem. But there are other limitations: many elements of screen drawing are still done on the CPU, and as largely serial architectures their ability to scale performance with dramatically higher resolutions is limited.

Some elements of drawing in Safari for example aren’t handled by the GPU. Quickly scrolling up and down on the AnandTech home page will peg one of the four IVB cores in the rMBP at 100%:

The GPU has an easy time with its part of the process but the CPU’s workload is borderline too much for a single core to handle. Throw a more complex website at it and things get bad quickly. Facebook combines a lot of compressed images with text - every single image is decompressed on the CPU before being handed off to the GPU. Combine that with other elements that are processed on the CPU and you get a recipe for choppy scrolling.

To quantify exactly what I was seeing I measured frame rate while scrolling as quickly as possible through my Facebook news feed in Safari on the rMBP as well as my 2011 15-inch High Res MacBook Pro. While last year’s MBP delivered anywhere from 46 - 60 fps during this test, the rMBP hovered around 20 fps (18 - 24 fps was the typical range).


Scrolling in Safari on a 2011, High Res MBP - 51 fps


Scrolling in Safari on the rMBP - 21 fps

Remember at 2880 x 1800 there are simply more pixels to push and more work to be done by both the CPU and the GPU. It’s even worse in those applications that have higher quality assets: the CPU now has to decode images at 4x the resolution of what it’s used to. Future CPUs will take this added workload into account, but it’ll take time to get there.

The good news is Mountain Lion provides some relief. At WWDC Apple mentioned the next version of Safari is ridiculously fast, but it wasn’t specific about why. It turns out that Safari leverages Core Animation in Mountain Lion and more GPU accelerated as a result. Facebook is still a challenge because of the mixture of CPU decoded images and a standard web page, but the experience is a bit better. Repeating the same test as above I measured anywhere from 20 - 30 fps while scrolling through Facebook on ML’s Safari.

Whereas I would consider the rMBP experience under Lion to be borderline unacceptable, everything is significantly better under Mountain Lion. Don’t expect buttery smoothness across the board, you’re still asking a lot of the CPU and GPU, but it’s a lot better.

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  • Ohhmaagawd - Sunday, June 24, 2012 - link

    It's a first step. There will be retina monitors in the future. Reply
  • Freakie - Monday, June 25, 2012 - link

    Lolwut... Monitors that have great quality color are already high resolution... They were pushing major pixels before it was popular ;) Reply
  • vegemeister - Monday, July 02, 2012 - link

    With the exception of the (discontinued and originally $10,000) IBM T221 and it's derivatives, no desktop monitor has resolution exceeding 2560x1600, and that resolution is only available in the 30" form factor. Reply
  • Solandri - Saturday, June 23, 2012 - link

    I have the lower-end version of that particular laptop ("only" a 1600x900 screen, 2x64 GB SSD). I wish I'd opted for the 1080p screen. 1600p wide isn't really enough to put two apps side-by-side. I do that all the time on my 1920x1200 external monitor though.

    The screen is a glossy TN panel, but is pretty much the best TN panel I've used. My desktop monitor is IPS so I can see its limitations. But when I'm using the Z in public, the most frequently comment I get is how beautiful the screen is. Sony also does a stellar job with their anti-reflective coatings. it's a glossy screen, but I almost never see reflections (except in sunlight). Colors are a bit too saturated, and the custom color profile I made tones it down. Unfortunately none of the reviews on it tested its gamut. But from photo editing, it's got a wider gamut than most high-end laptop displays I've seen. And it's blindingly bright too - perfectly usable in direct sunlight at max brightness. I rarely run it over half brightness.

    The quad-SSD was because the laptop came out before SATA3 SSDs were available (the SATA3 spec had only been finalized a few months prior). 2.5" SSDs were already hitting the limits of SATA2 (3 Gbps) and the only way to get around it was by putting multiple SSDs in a RAID 0 array. So that's what Sony did. The 4-SSD version benchmarks at 430-500 MB/s sequential read/write. Not too shabby in 2010 using 150 MB/s mSATA stick SSDs on SATA2.

    Optical drives are more a matter of preference. I end up burning a lot of DVDs so it's definitely convenient. But if you don't do that or watch movies, then yeah I can see it being superfluous. As much as I'd like to see media being distributed on USB sticks, their cost of $1-$2 for 4GB vs. a few cents for a DVD means it's not happening yet. Do note that the Z tops out at 2.9 pounds. It's lighter than the first and second gen Macbook Air despite having a DVD/Bluray drive. That's the second most common comment I get - "It's so light!"
    Reply
  • OCedHrt - Sunday, June 24, 2012 - link

    The 1080p panel on the Z is IPS. And it's not glossy - you don't have a glass on your laptop. I believe this is more for weight reasons than anything else. Reply
  • maratus - Sunday, June 24, 2012 - link

    No, it's not IPS. Reply
  • Solidstate89 - Saturday, June 23, 2012 - link

    You have to be the most ignorant jackass I've ever seen. You've basically never even heard of that product until now yet that doesn't stop you from making baseless accusation after baseless accusation.

    Get the fuck over yourself. And Windows has always handled resolution scaling better than OS X, and it still does.
    Reply
  • ananduser - Saturday, June 23, 2012 - link

    In 2010 Sony offered a 13" MBP equivalent with matte 1080p TN panel(like all the other macbooks). It had a BluRay built besides a quad raid SSD option(that still exists). The current Z has the video card inside an external dock, it is as slim as the thinnest ultrabook with a full voltage CPU. Reply
  • OCedHrt - Sunday, June 24, 2012 - link

    Sony offered it in 2008 :) Reply
  • OCedHrt - Sunday, June 24, 2012 - link

    You are not applying the correct context.

    1080p is okay because windows has DPI scaling - though I agree with Anand that this doesn't work with apps that aren't written correctly. But the same applies to OS X. OS X handles it better because of vector based UI.

    It is an IPS display with 92% color gamut that Anandtech called amazing. Don't even try to pretend it sucks: http://www.anandtech.com/show/5530/sony-vaio-z2-ev...

    Blu-ray is not a default option, it is an extra configuration that you'd have to pay for. This isn't Apple were talking about - even Sony has typically more options than Apple.

    Quad-SSDs. Yes. You need to remember that his happened back in 2008 when SSDs were not doing 500mb/sec. This was back when a quad SSD only netted you about 300mb/sec and before TRIM was prevalent.
    Reply

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