Dual Monitor weirdness, 6870 AMD

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May 12, 2011
XFX 6870 Dual Fan
  1. iMac
  2. MacBook
  3. MacBook Pro
  4. Mac mini
Classic Mac
  1. iMac
  2. Power Mac
Mobile Phone
  1. iOS
I'll try to describe this as best as I can.

Previously, I have an Apple Cinema 23" plugged into the DVI port of my 6870 card. I also have a Samsung 213T plugged using "passive" DP-DVI adapter. Everything works, dual monitors on during bootup, etc.

Then I bought a second Apple Cinema 23". I removed my 213T, used the same DP-DVI adapter, plugged in my ACD, and now I have (2) ACD. Everything works... until one day I rebooted my Hack, and lo and behold, this is what I see on my screen.


Then I get this in OSX.


Now, noticed, the font size and proportion of the text is correct. I'm just missing 5/6th are of the screen.

It was also blinking between white and the normal screen.


Caused me some panic, I thought my 6870 card became defective...

I thought my two monitors got fried, because prior to this reboot, we had a power failure. So I tried using my old standby Samsung 21" monitor... for a few reboots, it showed the same problem. Which made me think, it's really the 6870 that is the problem.

But then during another reboot, everything went back to normal.

But unfortunately, it's only normal if I have the Samsung 21" plugged in ONLY! I can get my ACD working if I plug it in after OSX is booted. But not before.

So I bought an Active DP-DVI Adapter. -- thinking this may solve my problem.
ACD #1 plugged to DVI port
ACD #2 using Active DP-DVI converter, plugged into DP port.
.... same stupid problem! The Active adapter didn't fix any of my problem.

The resolution of the ACD is 1900x1200, and the Samsung is 1600x1200.

And the weird thing is if I plugged ONLY the ACD to the DVI port, I still get the same problem. (This didn't used to be this way, before, it would boot up normally... It seems some setting/memory in the video card got changed or something, because now even with just (1) ACD plugged into the DVI port, I'm getting the same Clover screen and OSX screen problem above.)

The only way it seems to "reset" my 6870 card to not show this weird Clover screen and OSX problem is to plug in my old 1600x1200 res Samsung monitor.

So.... I setup for 3 monitors...
ACD #1 to DVI
ACD #2 using Active DP-DVI adapter, plugged into DP
Samsung using Passive DP-DVI adapter, plugged into DP

^^^ This is the only setup that would work where I don't get that giant Clover screen, and my OSX screen works. Of course, now I have 3 monitors on my desk... too much! But at least, all 3 monitors are showing and at full resolution and correct size. Just a slightly annoying thing is ACD#1 @ DVI port is totally black during the whole Clover/OSX boot up. It only comes alive when the OSX desktop shows up.

What I want to happen is just use (2) ACD screens. I can't seem to make this combination work.

--- things I haven't tried.
* Get another Active DP-DVI adapter and use both DP ports for the ACD
* change system definition, currently right now I'm using iMac 12,2

I need some guidance from others that encountered a similar problem (weird resolution, giant clover screen, etc). Right now, it seems my 6870 card only works properly if my Samsung monitor (1600x1200) is connected to it! Then the Clover boot screen and OSX desktop looks fine. If the Samsung isn't connected, I get the giant Clover boot screen you see above, and OSX screen doesn't work/look properly.
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