iMac mid 2010 graphics issues after installing Yosemite

Would you be willing to share your code so that I could compile and compare on my machine as well?

#include <stdio.h>
#include <stdlib.h>
#include <OpenCL/opencl.h>

#define BUF_SIZE        128

int main(int argc, char* const argv[]) {
        cl_uint num_devices, i, clock;
        char buf[BUF_SIZE];

        clGetDeviceIDs(NULL, CL_DEVICE_TYPE_GPU, 0, NULL, &num_devices);
        cl_device_id* devices = calloc(sizeof(cl_device_id), num_devices);
        clGetDeviceIDs(NULL, CL_DEVICE_TYPE_GPU, num_devices, devices, NULL);

        for (i = 0; i < num_devices; i++) {
                clGetDeviceInfo(devices[i], CL_DEVICE_NAME, BUF_SIZE, buf, NULL);
                clGetDeviceInfo(devices[i], CL_DEVICE_MAX_CLOCK_FREQUENCY, sizeof(cl_uint), &clock, NULL);
                printf("%s\t [%iMhz]\n", buf, clock);
        }
        free(devices);
}

Compile with:

gcc -framework OpenCL dumpcl.c -o dumpcl

Just complied and ran this and am seeing the same.

Fresh boot and waking up with power button

ATI Radeon HD 5750 [628Mhz]

Waking up with USB mouse/keyboard

ATI Radeon HD 5750 [157Mhz]

I already filled a problem report using the Yosemite beta's Feedback Assistant app.

So, now it's only matter of getting Apple to fix the **** thing.

Thanks to your dumpcl code, I've been able to confirm over the past few weeks that the behavior is indeed consistent. While rebooting totally ***** if I happen to have woken the Mac by mouse or keyboard, at least now it's understandable as to what's going on and that little bit of insight let's me rest just "that" much more.

We will likely get El Crapitan before we get a Yosemite fix if I were a betting man.

Anyone know if this bug is still present in 10.10.4?

Happy to report that since the logic board, power supply and video card were all replaced my video corruption has NOT resurfaced.

I think I should have posted in this thread, but I also am a gamer in a virtual game where I take photos of peoples Avatars and I have to download the photos to my Mac to work on in photoshop, then upload them back into the game.. since my upgrade to Yosemite I crash and cant do either...

here is my Org. post I didn't know how to move it over here... it shows the crash message I get on in my game.. when I try to save photo to my computer..

Yosemite is causing my virtual game not to work right

also noted that if i do wake the mac up with mouse/keyboard and the video clock is running at 157, putting it back to sleep and then waking up with the power button returns it to 628, meaning i don't have to go through a full restart.

I'm afraid the bug is still present with 10.10.4.

Will it ever be fixed Apple? Can't be that hard, can it?

I'd really like to know if they got the info about this, if they realise it's quite a big problem and why are they not doing a single thing...

It's a mystery to me...

It seems to be fixed in El Capitan! \o/

well that's encouraging! it's worth noting that my USB keyboard died and i switched back to the default bluetooth keyboard; the clock speed drop doesn't occur when waking up from bluetooth. looking forward to el capital and going back to the usb keyboard.

Really? Very interesting. I'm going to pop the beta on my iMac on another partition and see if it makes any difference. Very curious as I had thought it was a hardware issue rather than software.

Replying to myself...

I created a new partition, installed a beta of 10.11 on it and still saw the graphics corruption, particularly the menu bar was very corrupted. So for me, El Cap does not seem to address the issue. It was a very quick test, I may reboot the machine back into El Cap over the weekend and see how long it is before the non-menubar screen corruption happens, but I suspect it will be very quickly. Thus I don't believe what I am seeing is a software issue, but a hardware one.

Sadly, yes. It's probably a faulty gpu.

Agreed.

Graphics corruption (which is the actual start of this thread) I'm convinced is a GPU failure. I've experienced two of them, both fixed after the card was replaced. The first time I was good for a short while (month or two) and then it started up again. The second time, they replaced the graphics card (again) and the logic board. Since that fix, I've not experienced any more graphics corruption at all and have been rock solid.

The other issue that okrasit and I have been talking about is the incredibly sluggish graphics performance when the machine is woken via anything other than the power button. Clock speed goes from 628Mhz to 157Mhz. Putting the iMac back to sleep and then reawakening with the power button returns the clock speed to 628Mhz. THAT is a software issue and according to okrasit seems to (finally) be fixed in El Capitan.