Radeon Compatibility Guide - ATI/AMD Graphics Cards

[Fl0r!an]

Question:

hi, my radeon HD 5870 can't get higher than 1980x1080 on yosemite , but on windows I can get 2560x1080. whats the problem?

Explanation: According to official AMD specs (http://www.amd.com/de-de/products/graphics/desktop/5000/5870#), the HDMI port is limited to 1080p resolution. Not sure why, since it's a HDMI 1.3 port which should allow 1440p, but that's the official information and I think Apple has chosen to do a very strict implementation of this specification, while Windows allows to bypass the limitation.

Solution: Usage of an active DP->HDMI adapter allows resolutions up to 1440p (I think even 4K@30Hz will work this way). Be sure to use an active adapter, passive ones are limited to single link resolution (1080p).

 

[VioletDragon]

Oh so in order to use 3 or 4 Monitors with the 6870 i have to have 2x 6870s in my machine?

 

[Fl0r!an]

No, you have to use active display port adapters or native DP displays.

 

[VioletDragon]

So I've got to use an adaptor to use 2 Monitors on each of the two mDP Ports then? as HDMI and DVI gets no signal when just using 1 monitor on each Mini Display Ports.

 

[Fl0r!an]

You just need an active DP adapter, or use a true DisplayPort connection. It's a well known fact which occurs on every AMD GPU built in this decade (I think I even mentioned this in the first post of this thread).

 

[VioletDragon]

Cheers. Cant seem to find the Adaptors here in the UK which sucks tbh.

 

[Fl0r!an]

Those look fine to me: http://www.ebay.co.uk/sch/i.html?_f...layport.TRS0&_nkw=active+displayport&_sacat=0

 

[VioletDragon]

Adaptors looks good cheers. need to find one with either 2 DVIs or HDMI from one mDP port on the GPU. also I've got sleep working with the 6870 on my H61N-USB3. I'm using a DSDT to inject for my ATI 6870. sleep also works with my ATI 5450 also.

 

[VioletDragon]

Those look fine to me: http://www.ebay.co.uk/sch/i.html?_f...layport.TRS0&_nkw=active+displayport&_sacat=0

So I've been doing some googling around and I've found something called a MST Hub which is powered my 6870 has Mini Display 1.2 which can support up to 3 monitors from 1 Mini Display Port. I'm thinking of picking up one of these and testing it just wondering if OSX will like it tho worth a try?

http://www.amazon.co.uk/dp/B00JLRBC7S/?tag=tonymacx86-21

 

[Fl0r!an]

I don't know how well they are supported in OS X. Why don't you just use the physical ports on your card? You should be able to drive up to 4 displays by using 2 active DP adapters and 2 legacy connections (DVI/HDMI).