Topic Title: HD 7750 - flickering lines in 2D mode caused by low GPU/RAM clocks. How do I set the right clock settings?
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Created On: 11/06/2013 04:50 AM
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 11/06/2013 04:50 AM
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Hi guys. 

Some months ago I bought ASUS HD7750-1GD5. On the very first day I noticed some issues with this card. 

A few times a day I see a short horizontal flickering line (10-20 centimeters). It is about 1 pixel high and it flickers slowly and irregularly for 5-10 seconds, and then it goes away by itself. It does not depend on any particular application, I've noticed it in Skype, in Google Chrome, in PDF reader... 

There were no such issues with my previous AMD HD3650, nor with Intel HD 2000 integrated into i3 on my Gigabyte motherboard. I did not overclock, everything ran as out of the box. 

Nevertheless, the card seems rock stable, no BSODs, no artifacts when gaming. I'm using my PC for work, thus it is online for ~10 hours every day. 

Here are the specs of my system: 

Motherboard: Gigabyte ga-h67a-usb3-b3 

CPU: i3-2120 

GPU: ASUS HD7750-1GD5 

RAM: Kingston 4x2 = 8GB 

OS: Windows 7 Professional 64 bit 

PSU: Gigabyte Superb 550P

Video drivers: Catalyst 13.9 

In one forum I've read that various desktop artifacts might be caused by too low 2D clocks which are set by default for new AMD video cards. By default they are 300/150MHz, as reported by GPU-Z. 

To verify that the problem is indeed caused by low clocks, I launched ASUS GPU Tweak and went to 2D settings. I lowered clocks from 300 / 600 (notice - this is 4x frequency of GPU-Z, thus matching 150MHz) to 150 / 300 (75 on GPU-Z), and - yes - immediately I noticed multiple flickering 1px high horizontal lines appear on my screen. They went away after 5-10 seconds, but after that one of those lines started to appear much more frequently. Definitely, these problems are caused by low clocks, as they become more frequent if I lower the clocks even more.

As recommended in one forum for HD 7770, I set the frequencies to 500/800 MHz in AMD Catalyst overdrive profile (it took some profiles file tweaking because Catalyst does not offer 2D settings), verified in GPU-Z that the frequencies are set correctly. I worked in this mode for a week or so. I didn't notice those flashing 1px lines any more.

But now I'm getting another problem. Some seconds after I switch between various applications, entire screen flickers once for just a fraction of second, but still it freaks me out because it looks like my video has gone bye-bye. And one day I was watching a movie and suddenly the screen went black forever. I could hear the sound, the movie was playing, but the screen was black and I could not do anything. Keyboard/mouse actions did not help, Ctrl-Alt-Del did not help. I had to do hard reboot.

This leads me to think that my current 500/800 MHz combination is not stable. I tried lower freqs. I tried GPU/RAM speeds as 400/200 MHz, but for some weird reason CCC set the RAM to its default maximum of 115000. Obviously, some GPU/RAM clock combinations are not valid and they cause the GPU to pick some defaults.

Now, finally my questions:

1) Are there any rules for 2D clock settings? Some mandatory relation factor between GPU/RAM clocks or something like that?

2) How do I find stable GPU/RAM clock combination for my card to fix those flickering lines and avoid "black screens" and BSODs? Or maybe it can be fixed in some other way without tweaking those 2D clocks? I'm using my PC mostly for work, so stability is a must.

3) Another issue now is that I would like to keep the final overdrive mode enabled, but after reboot GPU-Z shows 300/150 MHza again. I have to open Catalyst and check that "Enable Graphics Overdrive" checkbox after each reboot to make my 2D profile active. Is there any way to force those 2D frequencies to stick between reboots?

 11/07/2013 03:40 PM
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Today I tried to set 400 / 200 (GPU / RAM) but for unknown reason GPU-Z keeps telling me that RAM is at 1150. Obviously, some GPU / RAM combinations don't work together. Why? Iis there any calculator to find out which combinations do work?

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