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Radeon HD 6870 Dual Mac Cinema Display resolution

Last response: in Graphics & Displays
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June 25, 2012 9:44:42 AM

Hi,

A friend has a Radeon HD 6870 card and is using it in a PC with dual Apple Cinema 30inch displays.

With one display connected we get full res but when two are connected we only get 1280x800 or, sometimes, 1920x1080. Latest drivers installed and using standard Apple Cinema Display cables.

Thanks for any help.
June 25, 2012 12:44:14 PM

One Apple Cinema 30inch display has a native resolution of 2560x1600 if you are trying to run two of these monitors in eyefinity mode you wont be able to get full resolution (5120x1600) on both since the HD 6870's max resolution is 2560x1600

Also I'm not sure what you mean by "standard Apple Cinema Display cables" if you mean your using two-dual-link DVI cables those are the right cables for a resolution of 2560x1600.
The problem is the 6870 only has one dual-link DVI port the other DVI port is a single-link DVI port.

Dual-link DVI is capable of 2560x1600 but, single-link DVI is only capable of 1920x1200 so even if your just trying to run the 2nd monitor in cloned or extended mode you wont be able to reach a resolution of 2560x1600.

Your HD 6870 should have a displayport or mini-displayport(s) these are capable of your monitors full 2560x1600 resolution. You could try using your video cards dual-link DVI port and one of these or if your 6870 has two mini-displayports like mine you could just use them both.

If your monitors don't have any displayport connections you will need to get a mini-displayport to dual-link DVI adapter or displayport to dual-link DVI adapter if your using a displayport and not the "mini" or two if your using both mini-displayports.

The Apple store sells them here: http://store.apple.com/us/product/MB571Z/A You can find cheaper and possibly better ones if you stay away from the Apple store, just make sure it's to "Dual-Link" DVI
June 25, 2012 2:34:28 PM

My 6870 has 2 Mini DP slots but my friends 6870 has just a single DP port. Hopefully you have Dual DP's that should be your preference
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June 25, 2012 4:11:42 PM

sl4y3r said:
My 6870 has 2 Mini DP slots but my friends 6870 has just a single DP port. Hopefully you have Dual DP's that should be your preference
Your right and it's always best to use the same type of connections from the video card to both monitors.

The only issue is that if his monitors don't have DP connectivity a mini-displayport to dual-link DVI adapter costs $75-$100 and if he buys two he would probably be better off just replacing his video card with another one that has two dual-link DVI ports
June 26, 2012 10:07:09 AM

Idonno said:
Your right and it's always best to use the same type of connections from the video card to both monitors.

The only issue is that if his monitors don't have DP connectivity a mini-displayport to dual-link DVI adapter costs $75-$100 and if he buys two he would probably be better off just replacing his video card with another one that has two dual-link DVI ports


Jeez! I just checked and all adaptors run for $75+ as u said, which is EXPENSIVE! Total waste of a beautiful screen not being able to run it at its Native Res. Good luck with that buddy.
June 26, 2012 10:25:19 AM

Idonno - thank you very much for the detailed and clear reply. Very much appreciated! You're right, I meant the Apple DVI cables (with the firewire and usb passthrough box I believe) as I'm aware some DVI cables might not be up to the job.

Ironically he's been using an much older Quadro card from his Dell to use both screens at native res.

I did previously try using a DVI->DP Adapter on the card end with the other connected to the DVI (and swapped around) with no luck - the card does have two DP's but I only have one adapter. If I get something working I'll post but I reckon he might be better off getting a new card. Thanks again for the replies.
June 26, 2012 10:37:42 AM

sbryson said:
Idonno - thank you very much for the detailed and clear reply. Very much appreciated! You're right, I meant the Apple DVI cables (with the firewire and usb passthrough box I believe) as I'm aware some DVI cables might not be up to the job.

Ironically he's been using an much older Quadro card from his Dell to use both screens at native res.

I did previously try using a DVI->DP Adapter on the card end with the other connected to the DVI (and swapped around) with no luck - the card does have two DP's but I only have one adapter. If I get something working I'll post but I reckon he might be better off getting a new card. Thanks again for the replies.


Does he game on those screens? Because the 6870(and Pretty much any single card) will be tortured to render games on dual screens with that resolution. If his objective is just movies and stuff I guess he can stick with his Quadro.
June 26, 2012 12:27:53 PM

sl4y3r said:
Does he game on those screens? Because the 6870(and Pretty much any single card) will be tortured to render games on dual screens with that resolution. If his objective is just movies and stuff I guess he can stick with his Quadro.


He does concept artwork - http://www.leadinglightdesign.com/

I believe when they update to Photoshop CS6 it's going to help to have the more powerful gxf card. A few of their machines were supplied with the 6870 card in it :( 


June 26, 2012 2:43:51 PM

Can't He use 1 DVI -D link and then get 1 converter ?So thats 1x$75 over using 2x Mini DP which is a $150
June 26, 2012 4:25:25 PM

sbryson said:
I did previously try using a DVI->DP Adapter on the card end with the other connected to the DVI (and swapped around) with no luck - the card does have two DP's but I only have one adapter. If I get something working I'll post but I reckon he might be better off getting a new card. Thanks again for the replies.
The problem is the DVI end of the adapter has to be dual-link DVI plus a DVI to DP adapter would have to use a dual-link DVI port on the video card to get the resolution of 2560x1600 so your still in the same boat with only one dual-link DVI port.

It's kind of confusing but dual-link DVI is still only one connector that looks exactly like a single-link DVI except it has more pins and if your looking at the side with the holes that the pins go into there is a good chance that you still can't see any difference since it may have a standard dual-link DVI receptacle just without all the holes filled with connectors.

And then there is the name "dual-link DVI" which to anyone hearing it at first brings up incorrect images of two separate DVI connectors when in reality it's only one. Whoever named that should have put down his bong first. :pt1cable: 

Then there's DVI-A (Analog), DVI-D (Digital) both in single & dual-link and DVI-I (Digital & Analog) also both in single & dual-link. Here's a link to an image that shows the difference: http://cdn.overclock.net/2/21/215b66d1_all-DVI-types.jp...

Honestly though if your friend doesn't plan on gaming a video card like this might be his best bet http://www.tigerdirect.com/applications/SearchTools/ite... That should work. I would check with Evga to make sure it's powerful enough to do what you want first.
!