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Multiple MST Hubs
https://www.wsgf.org/phpBB3/viewtopic.php?f=68&t=26980		 Page 1 of 1
Author:  epsjesse [ 04 Jan 2014, 02:02 ]
Post subject:  Multiple MST Hubs
I have:
3 Accell MST Hubs
1 Powercolor 7870 Eyefinity Card
windows 7 professional 64bit
the latest CCC drivers from AMD
Startech DP to HDMI - Active Adaptors

When I attach the 3rd hub, windows can only seem to output a max of 6 screens. In the display finder screens 7,8,9 are blacked out. When i attempt to "extend" the desktop to them windows crashes, does nothing or switches the outputs to 4,5,6,7,8,9 leaving 1,2,3 blacked out. I am using all the same screens and running them all at 1080.

It seems there might me either a limitation of 6 screens off of one graphics card or there is something i am missing??

Really hope i didn't waste money on something that is not possible! :doh:
Author:  Delphium [ 04 Jan 2014, 12:47 ]
Post subject:  Re: Multiple MST Hubs
Hi, I believe this is a limitation of the GPU, windows will allow you to configure 9 or 10 monitors, any higher than that, then you would need a 3rd party software like ultramon to manage the additional displays, so its not a limitation of windows, and must be down to either the GPU or the GPU drivers.

We know that AMD's drivers will only allow a maximum of 6 displays for use in Eyefinity, Eyefinity must also be run from a single card, not spanned across many like Nvidia, So it would appear that the remaining 3 displays would require an addtional GPU.

Not this would not allow these 3 screens to be entered into an Eyefinity group with any displays on the 1st GPU.

What are you trying to achieve exactly? A 3x3 video wall?
Author:  epsjesse [ 04 Jan 2014, 21:48 ]
Post subject:  Re: Multiple MST Hubs
Im going to try to get 8 screens working today, i didn't think to try that the other day. using 5 normal outs and 1 hub to get to 8.

I hope that there is not a limit of 6 outs per card. that would be dumb, the card handles 6 just fine, so at least 8 or 9 should go too. I'm not using it that hard, just to play back some video
Author:  Haldi [ 05 Jan 2014, 04:18 ]
Post subject:  Re: Multiple MST Hubs
there are always tricks to get more.

http://www.wsgf.org/forums/viewtopic.ph ... 76&start=0
Author:  Baldur [ 05 Jan 2014, 19:23 ]
Post subject:  Re: Multiple MST Hubs
AMD GPU chips from 5000-series onwards have contained 6 monitor outputs (all of which can be used for DP monitors, less for other types), which limits how many monitors you can drive, regardless of how many connectors the specific card has or how you plug MST hubs.
So 6 monitors is the maximum you can get out of one AMD card even with MST hubs.

Additionally DP bandwidth limits can limit you to less per DP port depending on display resolution and refresh rate of the connected displays.

Nvidia GPU chips from 600-series onwards have 4 monitor outputs.

Both manufacturers chips before those had 2 outputs (unless we go to really old stuff).

Each output needs specific hardware duplicated on the die itself, taking more die-space per output. So these 6/4/2 outputs/monitors per card limits are based on the GPU die hardware itself and cannot be bypassed except by additional hardware that makes several monitors show up as just one like in the linked forum post.

And even more for current 4k monitors: because of lack of high enough bandwidth DP monitor driver chips, all current 4k DP monitors contain internal MST hub and show up as two monitors to the OS, taking two of these GPU output slots.
Author:  LuckyNoS7evin [ 06 Jan 2014, 17:24 ]
Post subject:  Re: Multiple MST Hubs
Baldur - I thought current DP 1.2 had enough bandwidth for 4k and thought it was the scalers in the monitor that couldn't handle 4k yet.

Sent from my SM-N9005 using Tapatalk
Author:  Baldur [ 07 Jan 2014, 16:02 ]
Post subject:  Re: Multiple MST Hubs
LuckyNoS7evin wrote:
Baldur - I thought current DP 1.2 had enough bandwidth for 4k and thought it was the scalers in the monitor that couldn't handle 4k yet.

That was what I said, in somewhat bad way. Not sure which chip in the chain inside the monitors is the problem.
If DP 1.2 didn't have enough bandwidth, how would MST hub in the monitor help? :think:

Main result just is that each 4K monitor for now uses two GPU "monitor slots", instead of just one which is easily overlooked.
Author:  LuckyNoS7evin [ 07 Jan 2014, 16:09 ]
Post subject:  Re: Multiple MST Hubs
Baldur wrote:
LuckyNoS7evin wrote:
Baldur - I thought current DP 1.2 had enough bandwidth for 4k and thought it was the scalers in the monitor that couldn't handle 4k yet.

That was what I said, in somewhat bad way. Not sure which chip in the chain inside the monitors is the problem.
If DP 1.2 didn't have enough bandwidth, how would MST hub in the monitor help? :think:

Main result just is that each 4K monitor for now uses two GPU "monitor slots", instead of just one which is easily overlooked.


Ye it would teach me to read a bit better. You.said DP driver chips not DP ;)

Can't wait till they fix this.


Sent from my SM-N9005 using Tapatalk
Author:  wiak [ 24 Sep 2014, 09:50 ]
Post subject:  Re: Multiple MST Hubs
to say it simple
you cannot run more than 6 monitors without another card regardless, its also the maximum eyefinity allows, its a hell of a lot better than the old maximum limit of 2*
http://en.wikipedia.org/wiki/AMD_Eyefinity

HD 5000 series added support for 6 DP displays
HD 7000 series added support for HDMI and DVI together with DP displays, so you can use HDMI + DP + DVI etc

with the HD 7900+ series you can run 2x MST Hubs for a maximum of 6 displays from 2 DP ports on card
so if you want something like 12 displays you have to use two 7000 series cards that has 2 DP ports and 2 MST hubs

i hope this helps
just my two cents
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