Radeon R9 270 - cannot display HDMI and 2xDVI simultaneously. Hardware limitation or workaround?

[luger]

I have a Radeon R9 270 card with the following ports:
1 x DP
1 x HDMI
2 x DVI

I can get 2 monitors working on the 3 HDMI/DVI ports in any combination I want (HDMI and 1 DVI, HDMI and the other DVI, or 2 DVI), but I cannot get 3 monitors working simultaneously. All 3 monitors will show up in Windows Screen Resolution (Win 7) and in AMD CCC, but the display can be extended to only 2 of these monitors.

All the connections are direct to corresponding ports on the monitors, no adapters.

This is independent of whether I have a monitor connected to the DisplayPort port. So I'm guessing this is some kind of hardware limitation on these cards? Or is there some workaround that would allow me to run 3 monitors on the 1xHDMI and 2xDVI ports?

From this table, it seems there should be a way to connect 3 monitors using the DVI and HDMI ports:
https://community.amd.com/thread/231248

If you scroll down on the linked page, it shows:
R9 270X/270 max displays:
3 with DVI/HDMI *1
4 using DisplayPort *1
6 with an MST hub

Since the link to the table is no longer active, I don't know what the footnote is for the 3 displays with DVI/HDMI configuration.

 

[luger]

Figured it out. The card can support 3 monitors on the HDMI and DVI ports, but the catch is that the monitors connected to the DVI ports must be identical. That's what the missing footnote refers to.

All of my monitors are unique, so the card by itself is maxed out at 3 displays (1 on DP, 2 on the HDMI/DVI ports). To get to 4, 5 or 6 monitors, I need to use a MST hub.

 

[DeathReborn]

Figured it out. The card can support 3 monitors on the HDMI and DVI ports, but the catch is that the monitors connected to the DVI ports must be identical. That's what the missing footnote refers to.

All of my monitors are unique, so the card by itself is maxed out at 3 displays (1 on DP, 2 on the HDMI/DVI ports). To get to 4, 5 or 6 monitors, I need to use a MST hub.

On a R9 290 even 3 identical displays required the use of 1x DP, 1x DVI & 1x HDMI, the DVI ports share resources and is a physical imitation only solved by newer hardware (Graphics Card).

 

[VirtualLarry]

Yeah, only so many TMDS channels to go around between the DVI and HDMI ports; you can't use all three at once on those generation of cards. For more displays, you must use DisplayPort.

 

[luger]

On a R9 290 even 3 identical displays required the use of 1x DP, 1x DVI & 1x HDMI, the DVI ports share resources and is a physical imitation only solved by newer hardware (Graphics Card).

Not according to this table: https://community.amd.com/thread/231248
Looks like R9 290 should be able to handle 3 non-identical displays on DVI and HDMI ports (note there is no footnote on this configuration as there is with the R9 270; the footnote mentions the requirement that the DVI ports be connected to identical monitors). That table comes from AMD, so if you're in this situation, you should contact AMD.

 

[luger]

Yeah, only so many TMDS channels to go around between the DVI and HDMI ports; you can't use all three at once on those generation of cards. For more displays, you must use DisplayPort.

Yep.

I asked in the main graphics forum, but maybe you know the answer. Can MST hubs be daisy-chained? I.e., connect video card to MST hub. Connect another MST hub to the first MST hub. Possible so long as you stay under the 4 x 1920x1080 display limit?
thread here https://forums.anandtech.com/threads/possible-to-daisy-chain-mst-hubs.2573751/

 

[VirtualLarry]

Can MST hubs be daisy-chained? I.e., connect video card to MST hub. Connect another MST hub to the first MST hub. Possible so long as you stay under the 4 x 1920x1080 display limit?

That I can't tell you, I have no experience with MST hubs.

 

[DeathReborn]

Not according to this table: https://community.amd.com/thread/231248
Looks like R9 290 should be able to handle 3 non-identical displays on DVI and HDMI ports (note there is no footnote on this configuration as there is with the R9 270; the footnote mentions the requirement that the DVI ports be connected to identical monitors). That table comes from AMD, so if you're in this situation, you should contact AMD.

I have lon since gone past the 290's but they would only run 3x HP Pavilion 23xi displays (identical displays) using the DP. AMD are wrong in their information; shocking I know, but even with identical displays you cannot use DVI + DVI + HDMI on Rx 2x0 cards. Hawaii, Pitcairn, Tahiti all lack the hardware to supply those ports simultaneously, Tonga & Fiji both could.

As far as MST goes, some hubs you can daisy chain but it is hit and miss. I tried a few at work and Accell worked, Club3D & Sapphire didn't. Try both ports with the first hub in the chain, Accell only worked on the port 1 but port 2 would only work with a display.