Author Topic: 2011 iMac vs OpenCL  (Read 5423 times)


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2011 iMac vs OpenCL
« on: July 11, 2013, 09:45:44 PM »
Hi again,

I'm getting some mixed messages from PS when running it on a mid-2011 iMac (3.4 Core i7, Radeon HD 697M 2Gb). I'm running MacOS 10.8.4.

If I enable the Radeon in the OpenCL preferences, it does seem to contribute in a very small way to speeding things up, but in the console PS seems to be disabling it:

Using device: ATI Radeon HD 6970M, 12 compute units, 1024 MB global memory
max work group size 1024
max work item sizes [1024, 1024, 1024]
max mem alloc size 256 MB
selected 7 cameras from 7 in 0.00338 sec
Loading photos...
Reconstructing depth...
[CPU] estimating 1774x2277x288 disparity using 887x1139x8u tiles, offset -2
[GPU] estimating 2150x2317x576 disparity using 538x580x8u tiles, offset -379
GPU processing failed, switching to CPU mode

But further down in the log, it does appear to be using it in the build:

finished depth reconstruction in 514.051 seconds
Device 1 performance: 57.8953 million samples/sec (CPU)
Device 2 performance: 57.3216 million samples/sec (ATI Radeon HD 6970M)
Total performance: 115.217 million samples/sec
Generating mesh...
5467149 points extracted

Any ideas why this would be the case? Should I not be seeing a better boost from the GPU as well?
I've also run this on a newer iMac with the Nvidia GTX 680MX, and that one works wonderfully, almost cutting the geom build time in half.

Cheers, -Chad


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Re: 2011 iMac vs OpenCL
« Reply #1 on: July 11, 2013, 11:17:50 PM »
Chad, it seems that is a OSX problem, try this benchmark and let us know

as im read with help of google it seems that the cards are not supported ( OpenCL) under OSX, so propably you will need update OSX 10.8.4

Where can I download Mac OSX drivers?

Starting with OSX 10.5.x, AMD Radeon graphics drivers are included as part of the Apple MacĀ® OS X installation. Please update your MacĀ® OS X installation via Apple Update to ensure you have the latest available graphics driver.


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Re: 2011 iMac vs OpenCL
« Reply #2 on: July 12, 2013, 01:16:46 AM »
Yes, it would certainly not be a surprise that OSX is the reason behind the issue. Their support of graphics cards has been less than awesome over the years.

I couldn't download the benchmark link in that forum posting, but I did run another OpenCL one from LuxMark:

2011 iMac - Radeon 6970M : 390
2012 iMac - GTX680MX - 487

So they should not be very far off, certainly not to the amount I am seeing with PS. But from the history I have read through in the forums, it looks like the drivers can really make or break the GPU performance. In this case, it seems to be on the break end of the spectrum.