Update 5/15/2010: Valve released a new patch for Portal on the 13th which resolved the blurriness issue. Please see our update below for for the full details.

It’s been a while since anyone treated Mac OS X as a first-tier gaming platform, so when Valve announced that they would be bringing their Steam service and the Source engine to the Mac, it was big news. After a roughly 2 month beta period for the Mac versions of Steam and the Source engine, yesterday Valve finally released the first wave of their Mac gaming efforts.

As it stands Valve is taking a gradual approach to rolling out their back catalog to the platform. Even though Steam is out and the Source engine has been ported, this week has seen the release of only 1 Source game for the Mac: 2007’s critically acclaimed Portal.

While it’s not the most graphically intensive Source game these days (that title belonging to Left 4 Dead), at this point it’s as good as anything else for looking at the performance of the Source engine under Mac OS X, particularly considering how long it’s been since a game’s original developer did the Mac port. So with that in mind, we went ahead and took a quick look at Portal’s performance under Mac OS X.

As is the case with all of the games on the Source engine, they’re designed to scale up and down fairly well. With modern hardware though, we’re hard-pressed to keep older Source games from achieving runaway frame rates. So Portal performance is somewhat arbitrary – most Macs with a discrete GPU should be able to handle it to an acceptable degree.

The Test

For our test we loaded up our GPU test rig with Mac OS X 10.6.3 in a Hackintosh configuration. As Mac OS X does not currently support either the GeForce GTX 400 series or the Radeon HD 5000 series, we had to step back a bit with our video card choice, settling for a GeForce GTX 285. And while the use of a Hackintosh does technically invalidate our results since it’s not a real Macintosh, based on our experiments we believe that our results don’t suffer in any way for using a Hackintosh, and as such we believe the results to be experimentally valid. But of course, your mileage may vary.

CPU: Intel Core i7-920 @ 3.33GHz
Motherboard: Intel DX58SO (Intel X58)
Chipset Drivers: Intel (Intel)
Hard Disk: OCZ Summit (120GB)
Memory: Patriot Viper DDR3-1333 3 x 2GB (7-7-7-20)
Video Cards: NVIDIA GeForce GTX 285
Video Drivers: NVIDIA ForceWare 197.13
OS: Windows 7 Ultimate 64-bit
Mac OS X 10.6.3 "Snow Leopard"

Image Quality

We’ll start quickly with a look at image quality. Valve is traditionally a staunch Microsoft ally, having built up their services and engines around Windows and DirectX. For the Mac OS X port of Source, Valve had to replace the DirectX backend of Source with Mac-appropriate components, the key of which is OpenGL. Such a change can impact image quality depending on how it’s done.

Portal - Windows. Click to enlarge

Portal - Mac OS X. Click to enlarge.

We have a gallery of screenshots, but for our analysis we’ll stick with comparing in a single set. Going with 2560x1600 with the game at its highest settings and 4xAA/16xAF, to our surprise the images are distinctly different when directly compared. The Mac screenshot is noticeably foggier than the Windows image, and textures appear to be less sharp. It’s not a night & day difference, but the Windows screenshot is distinctly clearer than the Mac screenshot. Without a Windows reference image it would be harder to tell that the Mac screenshot differs this much, but we believe that the difference is great enough that anyone with an eye for details that has ever played Portal on Windows would notice the foggier/blurrier IQ on the Mac.

Now some of this can be explained away due to gamma, since Mac OS X and Windows have different default gamma levels, but gamma could never explain the entire difference. There’s clearly a difference in IQ between the Windows and Mac OS X versions of Portal, and it’s not in the Mac’s favor. It’s by no means bad, but as one person put this when being shown these screenshots “It’s like looking at a magazine scan” when looking at the Mac.


The other half of our quick look is at performance. The Macintosh platform is renowned for being a graphical powerhouse, but this refers to professional/prosumer photography and the like. For gaming, Apple has been slow to include support for new hardware and new driver features (they are just now OpenGL 3.0 compliant) and overall their drivers are more conservative when it comes to performance. Portal is going to be slower, the question is by how much.

We went ahead and ran a timedemo from test chamber 18 and beyond on both the Mac OS X and Windows versions of Portal. We kept the settings cranked up at all times, but varied the resolution between 1280x800 and 2560x1600 to look at different GPU loads. At the worst-case of 2560, the Mac version of Portal runs at only 54% of the speed of the Windows version. That moves to 63% at 1920x1200, and 66% at 1280x800.

Portal – like all Source engine games – is CPU limited when given a powerful enough GPU, and even with just a GTX 285 we can approach that under Windows. Under Mac OS X however, we look to be GPU limited at all times. The framerate never suffers as we’re always averaging more than 60fps, but we can easily turn off MSAA and AF to improve performance if we needed to.

Closing Thoughts

For Source engine enthusaists hoping to see the Mac OS X port of the Source engine meet the high standards of the Windows version, Portal presents a mixed bag. In our limited testing the Mac version of Portal doesn’t significantly suffer for being a port, but at the same time it can’t quite match the image quality of the Windows version. Feature-for-feature there is parity, but the Mac version just isn’t as sharp as the Windows version.

Performance isn’t any better. Portal is an easy game to run and so we’re largely being academic here, but the “tax” for Mac OS X is roughly a generation in hardware performance. For the performance we’re seeing on a GTX 285 under Mac OS X the results are similar to what we’d see under Windows with something like a 9800GTX. Given that at the high-end the Mac platform is also a generation behind in hardware, and you’re looking at 2008 performance for Portal even with the best hardware you can get today for a Mac.

Ultimately having the Source engine ported to Mac OS X is going to remove the technical need to use Bootcamp to run Windows for games, but based on Portal it doesn’t remove the need to boot Windows for performance reasons. For long-time Mac users none of this should be surprising, but it means that we shouldn’t expect the Mac OS X version of the Source engine to be revolutionary.

Update: 5/15/2010

On Thursday after we published our article Valve pushed out an update for Portal that focused on fixes for the Mac version. The big fix was the following:

Fixed screen "fuzziness" caused by color correction operation



This fixed the blurriness issue we saw with the initial version of Portal. Texture and geometry quality is now as sharp as it is under Windows. Performance remains unchanged, while there is still an image quality difference between the two due to lighting differences and a general degree of fogginess that still appears on the Mac OS X version.

Portal - Windows. Click to enlarge

Portal - Mac OS X w/Patch. Click to enlarge.



View All Comments

  • ltcommanderdata - Friday, May 14, 2010 - link


    It's probably a driver issue. These results are kind of old now, but Call of Duty 4 sees fairly comparable performance between the Windows and OS X versions on ATI GPUs like the HD 3870, but not nVidia GPUs. So OS X gaming performance doesn't have to be significantly less than Windows and it doesn't seem to be Apple's OpenGL implementation necessarily being slower. It's likely a matter of GPU driver optimization, particularly for nVidia GPUs which seem to be more inconsistent lately on OS X, Bioshock also had teething performance problems on nVidia GPUs in Snow Leopard until 10.6.2, and more optimization of the OpenGL code path in the Source Engine. It'd be great if you could compare Windows and OS X performance on an ATI GPU like the HD4870 to see if the results are different.

    I have a feeling GTX 285 drivers in particular may be less optimized than even other nVidia GPUs given the low user base since Apple doesn't actually ship it themselves as a BTO option. Perhaps Anand could try a comparison on his older MacBook Pro with a 9600M GT which should be mature now. The newer MacBook Pros probably use a special build of 10.6.3 and the 330M won't be supported by mainline OS X releases until 10.6.4 so probably won't be a good comparison platform since the drivers are probably immature as well.
  • Finally - Friday, May 14, 2010 - link

    Updates to Portal have been released. The updates will be applied automatically when your Steam client is restarted. The major changes include:

    Fixed screen "fuzziness" caused by color correction operation
  • zalves - Friday, May 14, 2010 - link

    As soon as I started to play portal on my Mac, I understood that the low performance couldn't be real. Directx is far more powerful and better suited for games, but just that. On a Mac the experience I had with steam was that I could still use spaces, exposé, and even the dashboard while playing with absolutely no delay! Reply
  • B3an - Friday, May 14, 2010 - link

    Congratulations. I've been doing that on Windows for atleast 5 years. Any half decent machine would.

    When someone plays a game though, they tend to .. you know... play the game, and not use the computer for other things at the same time. Mac is poor for this and always will be.
  • star-affinity - Friday, May 14, 2010 - link

    So, how one game (Portal) performs on the Mac can let us conclude things about the general performance of Macs?

    If you read my post above there are Mac version of games (much newer and supposedly more demanding than Portal) that run just as good as the Windows version.

    People are very quick at making conclusions – many times on very weak grounds.
    And humanity is supposed to be a clever species? Give me a break... :p
  • B3an - Saturday, May 15, 2010 - link

    I will bet you that all source games released by Valve will run considerably slower.

    And games are always faster on PC. For a start you get the latest hardware, and the latest drivers. With Apple you will have to wait for them even for drivers. Plus if you have a massive glitch or crashing in a game then your're screwed.
    And OpenGL just isn't as good as DirectX is these days, or the DX dev tools. Dev's use DX over OpenGL for a reason, even John Carmack who is IMO the best programmer around, has switched to DX and said this himself.
  • Zanfib - Friday, May 14, 2010 - link

    Valve updated Portal last night and one of the release notes mentioned a fix to correct "screen fuzziness". That might fix up your IQ issues....the performance is probably a more long-term, gradual fix, if it can be done at all. Reply
  • ShandyPants - Friday, May 14, 2010 - link

    Let's see… how many years experience have had Valve with the Windows/Direct3D platform? How many years of optimisation? How big a task is it to port the entire Source engine over to OpenGL? Lots and huge would be the answers. How long has Portal/Source and Steam been on the Mac/OpenGL platform? A few days, months at most.

    The Mac platform is poor for gaming because virtually nobody develops games for it, nobody develops games for it because it's a poor platform for gaming. Notice the circle? Never mind because Valve have noticed that it and that it's complete nonsense and unnecessary.

    With Macs being largely closed systems they could, within a few years experience from developers, easily match that of the higher end off-the-shelf Win systems (no point comparing to a self-built rig). Valve are working with known hardware configurations when it comes to Macs, you don't have this with Windows PCs since you can mix and match configs infinitely. This "known" situation will only aid performance (so long as graphics card devs and Apple get on board with optimisation).

    In my view the Portal results are an impressive start, 60FPS at 2560*1200 is nothing to complain about.

    As for the quality, again see above… but AnandTech should disable color correction because it's broken and turns things blurry.
  • B3an - Saturday, May 15, 2010 - link

    "With Macs being largely closed systems they could, within a few years experience from developers, easily match that of the higher end off-the-shelf Win systems "

    No they couldn't. And i've said most of this already but...

    No DirectX, which is overall better, and has better dev tools. This is why dev's choose to use it over OpenGL. As i mentioned above, even John Carmack of ID Software has now moved to DX because of this. No major games companies use OpenGL now if they have a choice to choose.

    Drivers: Most Macs run very out of data drivers, and you have to wait for Apple on this.

    PC's can also easily be overclocked, and there is tons of tweaking tools for PC gaming.

    OS: I could also argue that Windows is better suited for gaming aswell.

    Hardware: forget getting the latest GFX cards for mac. It's time "think different" and pay more for last years hardware.
  • B3an - Saturday, May 15, 2010 - link

    Oh heres another important factor: OSX does not support OpenGL 3.0, let alone 4.0 (latest version).
    OSX is two full revisions behind. OpenGL 2.0 is probably roughly equal to DirectX 9 at best.

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