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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  • Manni01 - Tuesday, July 17, 2012 - link

    Great review as usual, but I would really like to know how Anand was able to check if Speedstep and Turboboost worked. In the last Macbook review (2011), he used MSR Tools, but I could not get these to work on Lion on my June 2012 MBP 13. He remains very vague about how, although he does confirm this works as expected on the MBP 15r .
    This isn't my experience. I tried using Intel's MacCPUID in Lion, and a few other tools, and it looks like the CPU is locked at nominal speed (2.9GHz in my case), so neither speedstep nor Turboboost seem to work in Lion. They work as intended in Win7/Bootcamp, going down to 1GHz to save battery or up to 3.6GHz when only one core needs more power.
    So here are my questions:
    1) Anand please could you tell us which tools you have used?
    2) Has anyone tested this on the new macs (June 2012), using which tools, and what is the result?
    Speedstep definitely worked in Snow Leopard on my MBP 13 2011, so it must be a limitation in Lion.
    Reply
  • kenancagri - Thursday, July 19, 2012 - link

    It is very good article. I loved it. Thanks for Lal Shimpi. Reply
  • williamsj - Friday, July 27, 2012 - link

    Even the iPhone 4 is physically easier to maintain/upgrade than this thing.

    Check http://www.ifixit.com

    The worst maintainable piece of hardware they have ever looked at!!

    John
    Reply
  • Throckmorton - Tuesday, August 07, 2012 - link

    You didn't address whether pixel doubling is supported for games. IE rendering each pixel as 4 screen pixels. That's very different from upscaling, because with pixel doubling there's no blurring. Reply
  • Dubious1968 - Thursday, August 09, 2012 - link

    I've given up waiting for Apple to refresh the iMac, and am thinking of buying the Macbook Pro Retina instead. My only concern is that Apple should have equipped this laptop with a more powerful graphics card, given it is driving such a high res screen.

    I will be using it for Photoshop and HD video editing along with some gaming.

    Any help appreciated.

    Dubious
    Reply
  • sleddoggin - Saturday, August 11, 2012 - link

    So, I've done my best to read (skim) through all 46 pages of comments for this post, and have been reading other threads on more-or-less the same topic, so forgive me if I've missed something.

    I own a base model rMBP w/ 16mb ram (for safety), and am really quite unimpressed by openGL performance in games that were fluid (30-60fps ANYway) on my old Mac Pro 2006 w/ an ATI Radeon 5770 HD graphics card (I guess it helps, too, that the Mac Pro GPU is sitting in an x16 PCIe lane, not an x8, as with the rMBP). The Mountain Lion upgrade has been some improvement.

    When I first read Anandtech's article, I sort of thought, why not shut the lid on my MacBook Pro Retina, and plug in my old Apple Cinema display when I want to play games (I plan on using my desktop display when I'm at home for most stuff anyway). Then, the discreet NVIDIA GeForce GT 650M wouldn't be overworked by having to render all those extra pixels, right? Wrong. Gauging from the tests I've done, anyway, I'm getting the same choked performance on my relatively low-res external display (with the rMBP lid shut) as I do when I play those games on the rMBP screen (either at native OR scaled resolutions).

    So my question becomes, isn't this a software issue? Shouldn't the Apple/NVIDIA engineers be able to re-route ALL of that sexy mobile GPU processing power to a single, lower-res external display, and save us gamers the hassle of trading in our rMBPs for regular 2012 MBPs?

    This computer upgrade is really a no-brainer for me, otherwise. With the Thunderbolt ports, and the built in HDMI, I've been easily able to retire my old Mac Pro, and still keep my various displays (HDTV, etc.), and extensive array of USB/Firewire accessories fully operational. It just blows my mind that I get better gaming performance from my creaky old 2006 Mac Pro.

    Thanks for reading my contribution to this thread. Does my thought hold ANY water? I sure as heck don't want to give up this beautiful-looking piece of hardware if I don't have to...

    Cheers,
    -SledDoggin' (another reluctant Apple fanboy)
    Reply
  • vml_ - Saturday, August 25, 2012 - link

    Here's what I don't get and haven't seen answered anywhere. If there are performance issues at 1800p, can they be alleviated by downscaling (eg to 1080p)? Reply
  • S J - Friday, August 31, 2012 - link

    That sounds like great. good effort. Also have seen nice article on http://techinlead.com/apple-introducing-macbook-pr... Reply
  • LookupOEM - Saturday, September 22, 2012 - link

    maybe i'm wrong, but i always thought that OEM means "Original Equipment Manufacturer", a company that makes equipement that is sold by others under their own name.

    Toshiba making hard drives for Apple makes it an OEM, just as Intel, Samsung and others

    but, Apple IS NOT AN OEM, and there is no such thing as a PC OEM !!
    a PC OEM would be a company that supplies parts to build a PC, not the PC maker itself.

    did i miss something here ?
    Reply
  • Penzi - Thursday, October 04, 2012 - link

    Now that Mountain Lion has been out for a bit and several programs have been "retinized" are you planning on updating your review or crafting a mini-review that addresses changes, improvements and new caveats? I, for one, would love to hear about scrolling performance and resolution impact to common software (the OS and iWorks, FinalCut, etc), such as setting the display to "more space" (1920) and clocking the Safari FB news feed, and so on... Reply

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