I don't see why it's unreasonable to suggest that Apple would make more money with a elegantly designed box to convert HDMI to mini-displayport. I have two MacBook Pro's and a MacPro Octo. I'm plenty happy with Apple. I'm not pissed at them or anything.
You have to understand, within some circles of the Mac community its considered unreasonable to want anything other than exactly what Apple gives you.
You have to understand, within some circles of the Mac community its considered unreasonable to want anything other than exactly what Apple gives you.
I guess! I have never understood Apple's fascination with proprietary i/o; FireWire excluded. Maybe DisplayPort will enjoy wide adoption. I'm thinking back to the, what was it, Apple Display Connector? $99 for DVI. When they went to DVI, I was enthusiastic.
I guess! I have never understood Apple's fascination with proprietary i/o; FireWire excluded. Maybe DisplayPort will enjoy wide adoption. I'm thinking back to the, what was it, Apple Display Connector? $99 for DVI. When they went to DVI, I was enthusiastic.
Fanboy? Somewhat. Siccophant(sp?), not so much.
Two theories:
A) every so often Apple wants to impose its ideas on the display arenas and releases a new connector. Every time, however they have failed.
They want to do everything they can to restrict you into buying their own displays.
DisplayPort is the next big thing in PC land, the flagship ATI Radeon 5870, 5850 etc. DirectX11 cards all have DisplayPort and you need DisplayPort to drive
But the "mini"fying of DisplayPort, yeah, Apple likes to roll that way with their connectors sometimes... Can't say much wrong about Magsafe though... I bet you there are laptop companies out there dying to license or reproduce that technology. It in fact should be a new electronics standard while waiting for induction/wireless charging, etc. to become mainstream. WiFi for wireless, what about for charging wirelessly? I recommend the name WiPow. Wireless Power, get it! "WiPow certified"... OK sounds a bit silly, but so does "Magic Mouse". Maybe WiCharge. Or WiJuice.
Quote:
Originally Posted by hermes369
I guess! I have never understood Apple's fascination with proprietary i/o; FireWire excluded. Maybe DisplayPort will enjoy wide adoption. I'm thinking back to the, what was it, Apple Display Connector? $99 for DVI. When they went to DVI, I was enthusiastic.
Fanboy? Somewhat. Siccophant(sp?), not so much.
Quote:
Originally Posted by BenRoethig
Two theories:
A) every so often Apple wants to impose its ideas on the display arenas and releases a new connector. Every time, however they have failed.
They want to do everything they can to restrict you into buying their own displays.
It's Apple, master of sending out mixed messages. (See: AppleTV, MacMini, iMac, MacBook Aluminium pre-MacBook Pro 13", Cinema Display 24", 30"... and so on)
Quote:
Originally Posted by hermes369
I don't see why it's unreasonable to suggest that Apple would make more money with a elegantly designed box to convert HDMI to mini-displayport. I have two MacBook Pro's and a MacPro Octo. I'm plenty happy with Apple. I'm not pissed at them or anything.
Here's my deal. I don't have a flat screen TV yet. I'm anxious to get one; when I heard the iMac announcement about video in; I thought: no reason to buy a TV now. I imagine an HDMI hub maybe with a remote, maybe keyboard switched, maybe an iPhone remote for it, all terminating at the iMac on the wall. It seems there are other ways to accomplish a similar goal: Sling Box comes to mind. Still, I will want a console at some point and will want the lowest latency possible.
So, I don't particularly need another computer. For the same price, I could probably find a decent and larger flat screen of some description. Still, having an iMac as a family hub for any and all video inputs: super cool. I can't remember the last time I've posted here, I just read all this harassing stuff when the underlying point is valid: Apple might have gone ahead and taken this Beast to the next level.
DisplayPort is the next big thing in PC land, the flagship ATI Radeon 5870, 5850 etc. DirectX11 cards all have DisplayPort and you need DisplayPort to drive
But the "mini"fying of DisplayPort, yeah, Apple likes to roll that way with their connectors sometimes... Can't say much wrong about Magsafe though... I bet you there are laptop companies out there dying to license or reproduce that technology. It in fact should be a new electronics standard while waiting for induction/wireless charging, etc. to become mainstream. WiFi for wireless, what about for charging wirelessly? I recommend the name WiPow. Wireless Power, get it! "WiPow certified"... OK sounds a bit silly, but so does "Magic Mouse". Maybe WiCharge. Or WiJuice.
NO ONE in any of the forums has shown any proof that the 5870 display port out works with the imac 27'
One guy claimed he had it working and when everyone asked for photos he disappeared.
One guy claims his 5850 does not work though. (this is all using a mini dp to DP cable)
I do not think this display is working with even displayport equipped pcs.
The spec is the spec. DP signaling is the same as mDP signaling. Unless there is problem with the card, its driver or the cable, which is possible since this tech is still pretty new, then they will work.
The spec is the spec. DP signaling is the same as mDP signaling. Unless there is problem with the card, its driver or the cable, which is possible since this tech is still pretty new, then they will work.
If it did then it would be a fine thing. The fact that when using a DP to mDP cable the ATI 5800 series is currently incompatible with the mDP input on the Apple 24" LED is not encouraging.
If it did then it would be a fine thing. The fact that when using a DP to mDP cable the ATI 5800 series is currently incompatible with the mDP input on the Apple 24" LED is not encouraging.
Not exactly sure what you mean. As was said before, DP/MDP is interchangeable according to the specs. Do you have a link that shows that the DP on the ATI cards don't work on the iMac? Don't get me wrong, it SHOULD work but since Apple seems to be clearly intent on preventing people from using this display with anything but a MacBook I won't be surprised if there is really is a problem using the iMac with these cards.
Not exactly sure what you mean. As was said before, DP/MDP is interchangeable according to the specs. Do you have a link that shows that the DP on the ATI cards don't work on the iMac? Don't get me wrong, it SHOULD work but since Apple seems to be clearly intent on preventing people from using this display with anything but a MacBook I won't be surprised if there is really is a problem using the iMac with these cards.
I don't have anything regarding the iMac - links to 24" LED and ATI 5800 below.
Okay, so what are the practicalities of this thing in the real world.
If I want to use it as a second monitor, I plug my MBP in and what happens?
Do I have to boot the iMac in a special mode, like Target Disk mode or something? Or do I just boot the iMac normally, and connect it up. If so, what is the iMac doing in the background? Is it just sitting idling whilst I only really use its panel?
Also what happens if I plug a USB device into the iMac? Does it appear on my MBP's desktop? Probably not seeing as how there is not physical connection between the iMac and my MBP, except for the mDP cable. Is so, that means that I can't even plug a keyboard and mouse into the iMac and expect it to work with the MBP.
I'm a bit confused about how this whole video input breaks down in the real world...
NO ONE in any of the forums has shown any proof that the 5870 display port out works with the imac 27'
One guy claimed he had it working and when everyone asked for photos he disappeared.
One guy claims his 5850 does not work though. (this is all using a mini dp to DP cable)
I do not think this display is working with even displayport equipped pcs.
I bought the iMac 27" a week or so ago with the intention of using it also for an external display for my gaming winbox.....followed the forums and folks with limited knowledge of how exactly the iMac mdp in works.....seeing there are not yet any dvi=>mdp converter/scalers for the iMac decided to upgrade video card in winbox with ati HD 5870...ordered the mdp to dp cable from newegg http://www.newegg.com/Product/Produc...82E16812270262 and hooked the pc to the iMac.....for the curious, with the present ati drivers or some other incompatibility issue the iMac does not go into target display mode.....the iMac screen will go blue when command + F2 is used and then flash back to mac os on iMac....if you try the command a few times the iMac then will freeze up and a hard reboot is needed...so the assumption is correct that a pc equipped with dp ( my case the HD 5870 ) connected to the iMac 27" mdp does not at this time work...oh well, waiting for update on whether anything other than a Mac to Mac works
Okay, so what are the practicalities of this thing in the real world.
If I want to use it as a second monitor, I plug my MBP in and what happens?
Do I have to boot the iMac in a special mode, like Target Disk mode or something? Or do I just boot the iMac normally, and connect it up. If so, what is the iMac doing in the background? Is it just sitting idling whilst I only really use its panel?
Also what happens if I plug a USB device into the iMac? Does it appear on my MBP's desktop? Probably not seeing as how there is not physical connection between the iMac and my MBP, except for the mDP cable. Is so, that means that I can't even plug a keyboard and mouse into the iMac and expect it to work with the MBP.
I'm a bit confused about how this whole video input breaks down in the real world...
That does seem quite pathetic on Apple?s part. I understand that GPU they are using doing have this capability by default, but why even advertise it until you can get input to work effectively with DP. Unless there is a missing piece of the puzzle. Since I still haven?t seen any data on how the input is actually handled we can?t really say. They did have some initial driver issues with DP when they first added it to their machines.
Thank you for this. You just stopped me from ordering one.
I hate this BS with apple and having to struggle to get the "advanced" features to actually work.
I love the products but tired of the lack of support for the advanced user.
Quote:
Originally Posted by deja_vu
I bought the iMac 27" a week or so ago with the intention of using it also for an external display for my gaming winbox.....followed the forums and folks with limited knowledge of how exactly the iMac mdp in works.....seeing there are not yet any dvi=>mdp converter/scalers for the iMac decided to upgrade video card in winbox with ati HD 5870...ordered the mdp to dp cable from newegg http://www.newegg.com/Product/Produc...82E16812270262 and hooked the pc to the iMac.....for the curious, with the present ati drivers or some other incompatibility issue the iMac does not go into target display mode.....the iMac screen will go blue when command + F2 is used and then flash back to mac os on iMac....if you try the command a few times the iMac then will freeze up and a hard reboot is needed...so the assumption is correct that a pc equipped with dp ( my case the HD 5870 ) connected to the iMac 27" mdp does not at this time work...oh well, waiting for update on whether anything other than a Mac to Mac works
Thank you for this. You just stopped me from ordering one.
I hate this BS with apple and having to struggle to get the "advanced" features to actually work.
I love the products but tired of the lack of support for the advanced user.
The display is amazing to say the least and am willing to wait to be able to use as an external display for gaming rig......sure it will happen.
btw noticed something different with the sl upgrade to 10.6.2 and how the winbox ati Catalyst Control Center accepts the cmd+F2 from the imac...notice in the pic "System settings have changed. Catalyst Control Center is synchronizing. This may take several seconds." Though ati still does not recognize the iMac it is now trying and says so after the sl upgrade, this did not happen before the upgrade. The 2 monitors are both dells in pic but there should also be the imac..
noticed also that when cmd+F2 is pressed both the dell monitors and the iMac go completely black and while the iMac stays black the message above about syncing comes up on the dell displays.....after the sync fails all monitors return to normal...
think it is up to amd to start pumping out some compatible drivers and we might actually have something
Make sure you go to the official ATI forums and let them know the issues.
Have you tried the 9.11 beta drivers?
Also it has been confirmed the apple cinema display does not work on the 5XXX series but did on the 4xxx with the display port.
Quote:
Originally Posted by deja_vu
The display is amazing to say the least and am willing to wait to be able to use as an external display for gaming rig......sure it will happen.
btw noticed something different with the sl upgrade to 10.6.2 and how the winbox ati Catalyst Control Center accepts the cmd+F2 from the imac...notice in the pic "System settings have changed. Catalyst Control Center is synchronizing. This may take several seconds." Though ati still does not recognize the iMac it is now trying and says so after the sl upgrade, this did not happen before the upgrade. The 2 monitors are both dells in pic but there should also be the imac..
noticed also that when cmd+F2 is pressed both the dell monitors and the iMac go completely black and while the iMac stays black the message above about syncing comes up on the dell displays.....after the sync fails all monitors return to normal...
think it is up to amd to start pumping out some compatible drivers and we might actually have something
It was mentioned earlier in the thread. So far, everybody is trying to connect DP output to MDP input using a MDP to DP cable.
Of course I have no way of knowing this, but it may be possible that for some reason the available MDP-->DP cables do not also function in reverse as DP-->MDP cables.
I strongly suspect that this is the issue here, and that it's not the fault of the iMac or any DP output device.
And I also suspect the only reason the Atlona and Gefen DVI-->MDP converters don't work is that they don't support the iMac's resolution. Once Atlona or Gefen develop a dual-link resolution capable converter, I think we'll see things working as we would expect.
The 4xxx series cards were used successfully with this adapter with the 24'' inch cinema display via display port.
Quote:
Originally Posted by tonton
It was mentioned earlier in the thread. So far, everybody is trying to connect DP output to MDP input using a MDP to DP cable.
Of course I have no way of knowing this, but it may be possible that for some reason the available MDP-->DP cables do not also function in reverse as DP-->MDP cables.
I strongly suspect that this is the issue here, and that it's not the fault of the iMac or any DP output device.
And I also suspect the only reason the Atlona and Gefen DVI-->MDP converters don't work is that they don't support the iMac's resolution. Once Atlona or Gefen develop a dual-link resolution capable converter, I think we'll see things working as we would expect.
Comments
I don't see why it's unreasonable to suggest that Apple would make more money with a elegantly designed box to convert HDMI to mini-displayport. I have two MacBook Pro's and a MacPro Octo. I'm plenty happy with Apple. I'm not pissed at them or anything.
You have to understand, within some circles of the Mac community its considered unreasonable to want anything other than exactly what Apple gives you.
You have to understand, within some circles of the Mac community its considered unreasonable to want anything other than exactly what Apple gives you.
I guess! I have never understood Apple's fascination with proprietary i/o; FireWire excluded. Maybe DisplayPort will enjoy wide adoption. I'm thinking back to the, what was it, Apple Display Connector? $99 for DVI. When they went to DVI, I was enthusiastic.
Fanboy? Somewhat. Siccophant(sp?), not so much.
I guess! I have never understood Apple's fascination with proprietary i/o; FireWire excluded. Maybe DisplayPort will enjoy wide adoption. I'm thinking back to the, what was it, Apple Display Connector? $99 for DVI. When they went to DVI, I was enthusiastic.
Fanboy? Somewhat. Siccophant(sp?), not so much.
Two theories:
A) every so often Apple wants to impose its ideas on the display arenas and releases a new connector. Every time, however they have failed.
Two theories:
A) every so often Apple wants to impose its ideas on the display arenas and releases a new connector. Every time, however they have failed.
No offense but for a moment before I saw your username I assumed you were tekstud.
But the "mini"fying of DisplayPort, yeah, Apple likes to roll that way with their connectors sometimes... Can't say much wrong about Magsafe though... I bet you there are laptop companies out there dying to license or reproduce that technology. It in fact should be a new electronics standard while waiting for induction/wireless charging, etc. to become mainstream. WiFi for wireless, what about for charging wirelessly? I recommend the name WiPow. Wireless Power, get it! "WiPow certified"... OK sounds a bit silly, but so does "Magic Mouse". Maybe WiCharge. Or WiJuice.
I guess! I have never understood Apple's fascination with proprietary i/o; FireWire excluded. Maybe DisplayPort will enjoy wide adoption. I'm thinking back to the, what was it, Apple Display Connector? $99 for DVI. When they went to DVI, I was enthusiastic.
Fanboy? Somewhat. Siccophant(sp?), not so much.
Two theories:
A) every so often Apple wants to impose its ideas on the display arenas and releases a new connector. Every time, however they have failed.
I don't see why it's unreasonable to suggest that Apple would make more money with a elegantly designed box to convert HDMI to mini-displayport. I have two MacBook Pro's and a MacPro Octo. I'm plenty happy with Apple. I'm not pissed at them or anything.
Here's my deal. I don't have a flat screen TV yet. I'm anxious to get one; when I heard the iMac announcement about video in; I thought: no reason to buy a TV now. I imagine an HDMI hub maybe with a remote, maybe keyboard switched, maybe an iPhone remote for it, all terminating at the iMac on the wall. It seems there are other ways to accomplish a similar goal: Sling Box comes to mind. Still, I will want a console at some point and will want the lowest latency possible.
So, I don't particularly need another computer. For the same price, I could probably find a decent and larger flat screen of some description. Still, having an iMac as a family hub for any and all video inputs: super cool. I can't remember the last time I've posted here, I just read all this harassing stuff when the underlying point is valid: Apple might have gone ahead and taken this Beast to the next level.
One guy claimed he had it working and when everyone asked for photos he disappeared.
One guy claims his 5850 does not work though. (this is all using a mini dp to DP cable)
I do not think this display is working with even displayport equipped pcs.
DisplayPort is the next big thing in PC land, the flagship ATI Radeon 5870, 5850 etc. DirectX11 cards all have DisplayPort and you need DisplayPort to drive
But the "mini"fying of DisplayPort, yeah, Apple likes to roll that way with their connectors sometimes... Can't say much wrong about Magsafe though... I bet you there are laptop companies out there dying to license or reproduce that technology. It in fact should be a new electronics standard while waiting for induction/wireless charging, etc. to become mainstream. WiFi for wireless, what about for charging wirelessly? I recommend the name WiPow. Wireless Power, get it! "WiPow certified"... OK sounds a bit silly, but so does "Magic Mouse". Maybe WiCharge. Or WiJuice.
Good post.
NO ONE in any of the forums has shown any proof that the 5870 display port out works with the imac 27'
One guy claimed he had it working and when everyone asked for photos he disappeared.
One guy claims his 5850 does not work though. (this is all using a mini dp to DP cable)
I do not think this display is working with even displayport equipped pcs.
The spec is the spec. DP signaling is the same as mDP signaling. Unless there is problem with the card, its driver or the cable, which is possible since this tech is still pretty new, then they will work.
The spec is the spec. DP signaling is the same as mDP signaling. Unless there is problem with the card, its driver or the cable, which is possible since this tech is still pretty new, then they will work.
If it did then it would be a fine thing. The fact that when using a DP to mDP cable the ATI 5800 series is currently incompatible with the mDP input on the Apple 24" LED is not encouraging.
If it did then it would be a fine thing. The fact that when using a DP to mDP cable the ATI 5800 series is currently incompatible with the mDP input on the Apple 24" LED is not encouraging.
Not exactly sure what you mean. As was said before, DP/MDP is interchangeable according to the specs. Do you have a link that shows that the DP on the ATI cards don't work on the iMac? Don't get me wrong, it SHOULD work but since Apple seems to be clearly intent on preventing people from using this display with anything but a MacBook I won't be surprised if there is really is a problem using the iMac with these cards.
Not exactly sure what you mean. As was said before, DP/MDP is interchangeable according to the specs. Do you have a link that shows that the DP on the ATI cards don't work on the iMac? Don't get me wrong, it SHOULD work but since Apple seems to be clearly intent on preventing people from using this display with anything but a MacBook I won't be surprised if there is really is a problem using the iMac with these cards.
I don't have anything regarding the iMac - links to 24" LED and ATI 5800 below.
http://www.hardforum.com/showthread.php?t=1457486
http://discussions.apple.com/thread....94066&tstart=0
I would love it to work but like you wouldn't be surprised if it didn't.
If I want to use it as a second monitor, I plug my MBP in and what happens?
Do I have to boot the iMac in a special mode, like Target Disk mode or something? Or do I just boot the iMac normally, and connect it up. If so, what is the iMac doing in the background? Is it just sitting idling whilst I only really use its panel?
Also what happens if I plug a USB device into the iMac? Does it appear on my MBP's desktop? Probably not seeing as how there is not physical connection between the iMac and my MBP, except for the mDP cable. Is so, that means that I can't even plug a keyboard and mouse into the iMac and expect it to work with the MBP.
I'm a bit confused about how this whole video input breaks down in the real world...
NO ONE in any of the forums has shown any proof that the 5870 display port out works with the imac 27'
One guy claimed he had it working and when everyone asked for photos he disappeared.
One guy claims his 5850 does not work though. (this is all using a mini dp to DP cable)
I do not think this display is working with even displayport equipped pcs.
I bought the iMac 27" a week or so ago with the intention of using it also for an external display for my gaming winbox.....followed the forums and folks with limited knowledge of how exactly the iMac mdp in works.....seeing there are not yet any dvi=>mdp converter/scalers for the iMac decided to upgrade video card in winbox with ati HD 5870...ordered the mdp to dp cable from newegg http://www.newegg.com/Product/Produc...82E16812270262 and hooked the pc to the iMac.....for the curious, with the present ati drivers or some other incompatibility issue the iMac does not go into target display mode.....the iMac screen will go blue when command + F2 is used and then flash back to mac os on iMac....if you try the command a few times the iMac then will freeze up and a hard reboot is needed...so the assumption is correct that a pc equipped with dp ( my case the HD 5870 ) connected to the iMac 27" mdp does not at this time work...oh well, waiting for update on whether anything other than a Mac to Mac works
Okay, so what are the practicalities of this thing in the real world.
If I want to use it as a second monitor, I plug my MBP in and what happens?
Do I have to boot the iMac in a special mode, like Target Disk mode or something? Or do I just boot the iMac normally, and connect it up. If so, what is the iMac doing in the background? Is it just sitting idling whilst I only really use its panel?
Also what happens if I plug a USB device into the iMac? Does it appear on my MBP's desktop? Probably not seeing as how there is not physical connection between the iMac and my MBP, except for the mDP cable. Is so, that means that I can't even plug a keyboard and mouse into the iMac and expect it to work with the MBP.
I'm a bit confused about how this whole video input breaks down in the real world...
That does seem quite pathetic on Apple?s part. I understand that GPU they are using doing have this capability by default, but why even advertise it until you can get input to work effectively with DP. Unless there is a missing piece of the puzzle. Since I still haven?t seen any data on how the input is actually handled we can?t really say. They did have some initial driver issues with DP when they first added it to their machines.
I hate this BS with apple and having to struggle to get the "advanced" features to actually work.
I love the products but tired of the lack of support for the advanced user.
I bought the iMac 27" a week or so ago with the intention of using it also for an external display for my gaming winbox.....followed the forums and folks with limited knowledge of how exactly the iMac mdp in works.....seeing there are not yet any dvi=>mdp converter/scalers for the iMac decided to upgrade video card in winbox with ati HD 5870...ordered the mdp to dp cable from newegg http://www.newegg.com/Product/Produc...82E16812270262 and hooked the pc to the iMac.....for the curious, with the present ati drivers or some other incompatibility issue the iMac does not go into target display mode.....the iMac screen will go blue when command + F2 is used and then flash back to mac os on iMac....if you try the command a few times the iMac then will freeze up and a hard reboot is needed...so the assumption is correct that a pc equipped with dp ( my case the HD 5870 ) connected to the iMac 27" mdp does not at this time work...oh well, waiting for update on whether anything other than a Mac to Mac works
Thank you for this. You just stopped me from ordering one.
I hate this BS with apple and having to struggle to get the "advanced" features to actually work.
I love the products but tired of the lack of support for the advanced user.
The display is amazing to say the least and am willing to wait to be able to use as an external display for gaming rig......sure it will happen.
btw noticed something different with the sl upgrade to 10.6.2 and how the winbox ati Catalyst Control Center accepts the cmd+F2 from the imac...notice in the pic "System settings have changed. Catalyst Control Center is synchronizing. This may take several seconds." Though ati still does not recognize the iMac it is now trying and says so after the sl upgrade, this did not happen before the upgrade. The 2 monitors are both dells in pic but there should also be the imac..
noticed also that when cmd+F2 is pressed both the dell monitors and the iMac go completely black and while the iMac stays black the message above about syncing comes up on the dell displays.....after the sync fails all monitors return to normal...
think it is up to amd to start pumping out some compatible drivers and we might actually have something
oh well again....still waiting
Have you tried the 9.11 beta drivers?
Also it has been confirmed the apple cinema display does not work on the 5XXX series but did on the 4xxx with the display port.
The display is amazing to say the least and am willing to wait to be able to use as an external display for gaming rig......sure it will happen.
btw noticed something different with the sl upgrade to 10.6.2 and how the winbox ati Catalyst Control Center accepts the cmd+F2 from the imac...notice in the pic "System settings have changed. Catalyst Control Center is synchronizing. This may take several seconds." Though ati still does not recognize the iMac it is now trying and says so after the sl upgrade, this did not happen before the upgrade. The 2 monitors are both dells in pic but there should also be the imac..
noticed also that when cmd+F2 is pressed both the dell monitors and the iMac go completely black and while the iMac stays black the message above about syncing comes up on the dell displays.....after the sync fails all monitors return to normal...
think it is up to amd to start pumping out some compatible drivers and we might actually have something
oh well again....still waiting
Of course I have no way of knowing this, but it may be possible that for some reason the available MDP-->DP cables do not also function in reverse as DP-->MDP cables.
I strongly suspect that this is the issue here, and that it's not the fault of the iMac or any DP output device.
And I also suspect the only reason the Atlona and Gefen DVI-->MDP converters don't work is that they don't support the iMac's resolution. Once Atlona or Gefen develop a dual-link resolution capable converter, I think we'll see things working as we would expect.
It was mentioned earlier in the thread. So far, everybody is trying to connect DP output to MDP input using a MDP to DP cable.
Of course I have no way of knowing this, but it may be possible that for some reason the available MDP-->DP cables do not also function in reverse as DP-->MDP cables.
I strongly suspect that this is the issue here, and that it's not the fault of the iMac or any DP output device.
And I also suspect the only reason the Atlona and Gefen DVI-->MDP converters don't work is that they don't support the iMac's resolution. Once Atlona or Gefen develop a dual-link resolution capable converter, I think we'll see things working as we would expect.