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Old 04-07-11, 10:47 AM   #1
prefect42
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Default ConnectedMonitors and DisplayPort

I have a CentOS 5.5 machine (260.19.44) with a pair of Quadro FX 3800 cards. Connected are two monitors via DVI, and two monitors via DP. If I turn all the monitors off, and restart X, only the two DVI monitors are configured, and the two DisplayPort monitors are disabled.

This is true even if I use:

Option "ConnectedMonitors" "DFP-0, DFP-3"

Any suggestions as to how I can make this work such that there are always four monitors enabled irrespective of how many are currently powered on?

I have an ugly hack workaround but it's not a perfect solution... Wire in the monitors with USB cables, and use udev to trigger an X restart when a monitor is powered on and nvidia-settings says there are less than four monitors

There really is a somewhat valid reason why I want this...

jh
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Old 04-08-11, 04:02 PM   #2
danix
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Default Re: ConnectedMonitors and DisplayPort

I believe DisplayPort link training requires active participation from both the source and the sink, so I'm not sure if this can be made to work if the display won't engage in link training when it's off.

Have you tried passive DP->DVI dongles?
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Old 04-09-11, 04:56 AM   #3
Xevious
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Default Re: ConnectedMonitors and DisplayPort

Sounds like what you need is a 'dvi detective' except a displayport version. Unfortunately I don't know of any that exist =(
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Old 04-12-11, 04:16 AM   #4
prefect42
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Default Re: ConnectedMonitors and DisplayPort

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Originally Posted by danix View Post
Have you tried passive DP->DVI dongles?
These are only good for low resolutions as far as I'm aware (single link DVI). I'm running 2560x1440@60Hz so need dual-link. Active DP-DVI dongles are about 80 quid a pop. These monitors form part of a number of display walls, so I'd need quite a few.
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Old 04-14-11, 01:31 PM   #5
danix
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Default Re: ConnectedMonitors and DisplayPort

Yes, unfortunately passive dongles only support single link. To do what you want with active dongles, I'm pretty sure the dongle would have to allow link training even if a display device isn't connected. I'm not sure if there are any existing active dongle designs that do this.
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Old 04-14-11, 01:39 PM   #6
Xevious
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Default Re: ConnectedMonitors and DisplayPort

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Originally Posted by prefect42 View Post
These are only good for low resolutions as far as I'm aware (single link DVI). I'm running 2560x1440@60Hz so need dual-link. Active DP-DVI dongles are about 80 quid a pop. These monitors form part of a number of display walls, so I'd need quite a few.
I bought one of the dell OEM (bizlink) ddual link DVI active adapters for pretty cheap from a seller in texas for ~$50 shipped:

http://cgi.ebay.com/Bizlink-DisplayP...item415711c342

Found this seller in the UK selling them pretty cheap too:

http://cgi.ebay.com/BizLink-DisplayP...item256244fa54
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Old 04-14-11, 01:49 PM   #7
prefect42
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Default Re: ConnectedMonitors and DisplayPort

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Originally Posted by Xevious View Post
Found this seller in the UK selling them pretty cheap too:

http://cgi.ebay.com/BizLink-DisplayP...item256244fa54
Many thanks for the link, that is much cheaper than I'd found. Would this *definitely* solve the problem? That is, without a powered on monitor attached but with this I'd be able to force it into thinking it did?

jh
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Old 04-14-11, 01:51 PM   #8
Xevious
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Default Re: ConnectedMonitors and DisplayPort

Quote:
Originally Posted by prefect42 View Post
Many thanks for the link, that is much cheaper than I'd found. Would this *definitely* solve the problem? That is, without a powered on monitor attached but with this I'd be able to force it into thinking it did?

jh
Hard to say for sure, you would have to buy one and test it.

That + a DVI detective I would say certainly would solve the problem. I would say its likely but not for sure in this case.
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Old 04-14-11, 01:53 PM   #9
prefect42
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Default Re: ConnectedMonitors and DisplayPort

Quote:
Originally Posted by danix View Post
Yes, unfortunately passive dongles only support single link. To do what you want with active dongles, I'm pretty sure the dongle would have to allow link training even if a display device isn't connected. I'm not sure if there are any existing active dongle designs that do this.
If I was running a newer X server, would XRandR be able to dynamically add the display back in? That way I could have a udev trigger that just seamlessly rearranged the display.
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Old 04-14-11, 01:56 PM   #10
prefect42
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Default Re: ConnectedMonitors and DisplayPort

Quote:
Originally Posted by Xevious View Post
Hard to say for sure, you would have to buy one and test it.

That + a DVI detective I would say certainly would solve the problem. I would say its likely but not for sure in this case.
Sure, I was just thinking along similar lines. It was much simpler when I built this with DVI (apart from the weight of 28 3-5M DVI leads...).

jh
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Old 04-15-11, 03:31 PM   #11
danix
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Default Re: ConnectedMonitors and DisplayPort

Quote:
Originally Posted by prefect42 View Post
If I was running a newer X server, would XRandR be able to dynamically add the display back in? That way I could have a udev trigger that just seamlessly rearranged the display.
The NVIDIA X driver only supports XRandR up to version 1.1, which I don't think has this functionality.

However, you could probably wire up your udev trigger to an NV-CONTROL client that does this.
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