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.

Achieving Retina Boot Camp Behavior & Software Funniness
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  • orthorim - Wednesday, June 27, 2012 - link

    A very high resolution display is not a retina display - totally different thing.

    Retina is a special mode where each logical pixel is made up of 4 physical pixels, and special support for fonts and images.

    It's a huge step to go from 1:1 logical : physical pixels to a different factor. It's like bitmap based fonts vs. points-based vector fonts.

    Maybe a lot of PC manufacturers just don't get that?
    Reply
  • vegemeister - Monday, July 02, 2012 - link

    Apple is not using a PPI independent UI for their high-res displays though. There's a separate set of assets at 2x resolution, and programs that don't acknowledge that they're rendering at 2x resolution get upscaled.

    A real PPI independent UI, such as Gnome 2, uses vector resources for everything and allows applications to query the PPI of the display so they can render at appropriate dimensions.
    Reply
  • maraboshi - Saturday, June 30, 2012 - link

    and still that was FAIL because it runs Windows and not a brilliant OS like the Apple one...when will you stupid Apple haters will understand the fucking difference????? Reply
  • gbanfalvi - Sunday, July 01, 2012 - link

    I have it. It's a piece of crap. It feels like they just stuffed everything they could in this device without thinking.

    The pads on the bottom fell of from the heat.
    The battery died seven months in.
    The trackpad starts glitching regularly (not to mention it's terrible in general).
    The 1080p screen gets lines across it.
    The laptop overheats when I put it in speed mode.

    Evidence: https://dl.dropbox.com/u/245279/Photos/Photo%20201...
    Reply
  • azaat07 - Friday, July 13, 2012 - link

    Hole in your hyperbole...

    Only option is Intel Graphics 4000, shared memory.

    Intel 4k graphics are on par with 2007 discrete.

    Andrew
    Reply
  • woodsielord - Sunday, July 15, 2012 - link

    I have the said computer. I bought it with very high expectations, and the screen is still amazing, but the rest of the hardware keeps causing trouble. I have lived without my computer 3+ months due to repairs, and currently I'm typing this from my girlfriend's Zenbook (which, on the other hand, is zero problems and all play).

    The lack of international Sony support and the proclimity to hardware failure rule out Sony of all my future purchases. Many times I said to myself that I should have bought a MBP instead. If Sony stopped spewing forth so many products and instead tended to the details of flagship products and cared about its customers, it might have worked.
    Reply
  • mark3785 - Saturday, September 08, 2012 - link

    Ok, I'll play the fanboy…

    This is where Apple haters really get pissed (and as an Apple fan from the mid 80s (and a loyalist from the 90 days from bankruptcy days) (if I'm playing the fanboi thing I may as well go whole hog) I really start to chuckle).

    The MacBook Pro with retina display is proof positive that Apple can do things that the windows community can't because Apple has control of both sides of the coin, the hardware and the OS, plus (and this is a really huge plus) they have some very smart people working for them. It's one thing to put a hires display on a computer and an entirely different thing to make that display resolution independent. Sony may have come out with a hires laptop back in 2010, but they didn't do anything interesting with it.

    Eventually 2880x1800 will be run of the mill and higher resolutions will start to dominate. It isn't the number of pixels, it's how the system uses them to it's best advantage. This is (hopefully) the beginning of a new trend.

    BTW, one helluva review! Reviews are boring, though comforting when they state the obvious (yes, you bought a nifty machine, pat on the head) but a review this informative and complete just reinvigorates my interest in the hobby.
    Reply
  • Targon - Saturday, June 23, 2012 - link

    You need to look at the different price points that machines are sold for before you make statements like that. Most manufacturers see far greater volumes in the $500 range than they see in the $1500+ range, and it is that range that the majority of consumers look when it comes to buying a computer, either desktop or laptop.

    The area that manufacturers SHOULD be moving in is to make the move to a 1920x1080 display across their entire range of 14 inch and greater machines as the norm, rather than as an extra feature that people need to pay extra for if you are in the $450+ price range. Higher resolutions should be offered as the norm for higher end laptop displays. Until that happens, the PC side of the industry will seem to be inferior when it comes to display technology.

    If you think about it, display technologies have been fairly stagnant except from Apple, and we have not seen an aggressive attempt to improve what we see out there. 1920x1080 displays have been the norm for too long, and going to 1920x1200 isn't enough.
    Reply
  • OCedHrt - Sunday, June 24, 2012 - link

    Check out the new Sony TT Reply
  • vegemeister - Monday, July 02, 2012 - link

    1920x1080 should be the norm for 11". Reply

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