I have previously run Xplane X on a PC.  My good wife, who is a “Mac person” (more than I) bought me a new iMac Retina with a 5k screen so that my simulation programs would look more clear.  (I should add that I also make home videos and have fun with photography, which may be more suited to the new mac..)

 

Thanks to ironmaiden and benrussell here who has been helpful in getting me this far in migrating my XPX from a PC platform to a Mac.  This migration has raised the obvious performance comparison, and as well as getting any pointers from the user-base here on equalizing performance, I'm hoping that this comparison and any solutions might help other Mac users.

First to define the systems involved:  The PC is homebuilt by myself, a 2700K i7 processor, 8GB system memory (both not overclocked, CPU at 3.5GHz), GTX780 with 8GB DDR5 memory, Windows 8.1 64 bit, monitor is 1080p, which is the desktop resolution (1920X1080).

The Mac is a new iMac Retina (27-inch 5120 x 2880)  with a 5k screen.  Desktop resolution is 2560X1440, set as default but changeable.  The iMac comes with upgraded options of a "4 GHz Intel Core i7”  processor, 32GB of "1600 MHz DDR3" system memory, GPU is a "AMD Radeon R9 M295X" with 4GB DDR5 vram.  OS is Yosemite.

Both systems were restarted immediately before making the comparisons.  I have launched no other apps but do not know what system loads are put on each machine in background apps automatically started.

XPX in both cases is updated to 10.31 and run in 64 bit.  After installing from the media and updating, I moved the folders from the PC to the Mac apps, which includes add-ons such as SkyMaxx (latest version), UrbanMaxx, and updated runway textures.  (In copying over the folders the only one that I excluded was the Resources/Shaders, since I assumed they should be different).

I also run the haze.lua add-on, with identical settings on both machines, and with the .txt files on the Mac in the XPX root directory where the Mac looks for them. 

The scenario on both systems is KSEA, runway 16L, with "Daytime" and "Clear" set in the startup screen.  The aircraft is the stock Baron in 3D panel view.  The iMac has controllers connected and the USB dongle.  The PC has neither. AI traffic is set to 0 for both systems.

 

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The rendering screen, identical for both systems, is shown here:

 

http://www.fsfiles.org/flightsimshotsv2/images/2014/12/29/ayNO1.png    

 

Well- not quite identical, since the use of NO full screen means (as I understand it) that XPX has a resolution equal to that of the desktop,  which (as indicated above) is higher on the Mac (2560X1440 Mac vs 1920X1080 PC).  I'm not sure what performance penalty is imposed on the Mac by that different desktop resolution.  If there is any extrapolation between resolution and performance for XPX that would be good to know, although differences in system architecture might make that a moot point.

 

Screenshots of XPX in the scenario described above are shown for the PC:

 

http://www.fsfiles.org/flightsimshotsv2/images/2014/12/29/rTHh.png     Frame rate is 28.76

 

.....and the Mac

 

http://www.fsfiles.org/flightsimshotsv2/images/2014/12/29/TbLNe.png  Frame rate is  10.28, or 19.9, not sure what the difference between f-act and f-sim is....

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In an attempt to equalize XPX resolution, I put the iMac XPX into Full Screen mode and selected 1920X1080.  Frame rate is 17.2 f-act,  19.9 f-sim.  Nothing as good as the PC, although now XPX output resolutions should be similar.

 

I'd be interested in any recommendations in enhancing the iMac performance, if possible, and maybe this is helpful or interesting to someone else.

 

Thanks,  Bruce.

 

 

 

f-act is graphics frame rate achieved.

 

f-sim is physics frame rate achieved.

 

 

When you go under ~20 the flight model keeps running faster than the graphics output.

This keeps the control response reasonable* even though your screen displays as a slideshow.

 

 

*Extremely light/heavy aircraft may become unusable. As will anything with extremely stiff landing gear setup, which may include helicopters.

The GPU on the Mac is being hit more.  This could be Driver .

 

What is the GPU on the PC ?

In general, nVidia graphics cards are better for XP and FSX than Radeon.  Keep drivers up to date and maybe Radeon will improve.  Also, increased screen resolution forces the graphics card to handle more pixels at a time which is a framerate killer regardless of the VRAM.  Compare the systems at the same resolution (which largely negates the advantge of the "better" screen on the Mac.)  There may also be a penalty for not using "native" resolution on the Mac screen.  I'd use the Mac for photos and videos, and use the PC where it runs sims better.  As you know from photography, higher resolution does not necessarily mean better as an image is scaled up.

Radeon R9 M295X is a mobile GPU, which is quite similar to the R9 280X desktop GPU. From a graphics standpoint this is quite a downgrade from your GTX 780.

Radeon R9 M295X is a mobile GPU, which is quite similar to the R9 280X desktop GPU. From a graphics standpoint this is quite a downgrade from your GTX 780.

 

yes.

 

how the heck i did not read that M

Thanks for the replies and comments.....  they are what I had already figured out myself given the results of the tests that I did.  I'd still be interested if anyone is using a similar Mac and getting better results.  I have all of my controllers working through a USB hub, which in turn goes to a USB switch, then to the PC and iMac, so can apply the controllers to either machine.....  although without physically moving monitors around I only get to look at one "head-on"... 

 

I never expected XPX to work in 5k, but see that it can get to 4k in full screen on the iMac (or I can get the iMac desktop to 4k and use "windowed mode").  I was expecting some better texture resolution in XPX as a result of the higher display res, but the fps sure takes a lot out of the immersion when it falls to a perceptable point.  The other solution, obviously, is to get a 4k PC monitor and get to a higher XPX res that way, with the benefit of being able to overclock and generally interact with the PC to drive things harder.

 

Thanks again, and happy new year to everyone.

 

Bruce.

This is sort of why I wasn't personally excited about the Retina iMac - Stunning screen, but hamstrung by GPU choice.

 

Not sure whey then insist a desktop needs to be so thin, as they could have made it a bit thicker and put a WAY better GPU option on the BTO options.