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E6420 nVidia 4200: video output off PRO3X port replicator


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Please someone can guide me for dual monitor setup for Dell e6420 with PRO3X port replicator.


I installed El capitan on my e6420 and is working fine. But it does not support external monitors connected to the Docking station.


USB devices connected to Docking station are working fine including Ethernet connection, keyboard , mouse.


I really need to get external monitors to work with Docking station.


I appreciate , if anyone could help me to get this done.Optimus is disable in BIOS.


Thank you in advance and appreciate your time and help.

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Hello Herve,


Appreciate your efforts and Time.


May be if time permits , you can help me with this problem.I have tried to follow few suggestions found on forum as well other sites , but could not get the solution.


The scenario is this. With the help of user from Multi boot computer system , I have 3 OS running on e6420. OSX-el Capitan, W10 and Suse Linux.


All above 3 OS runs fine and are with Optimus disabled.


Docking station is PRO3X. post-100830-0-50109500-1485910353_thumb.jpg


With Optimus disabled . Win-10 and Suse Linux supports 2 monitors connected to DVI ports with no problems but OSX does not support any external monitor connected to Docking station.


If Optimus option is enabled , Win-10 and Linux , supports only 1 external  monitor connected on DVI port but no support from OSX to any external monitor.


with Optimus enabled , linux supports 1 monitor but system works very very slow almost crawling with sticky mouse response. Certainly Optimus is not well supported in Suse linux either.


Then I tried Ubuntu 16.04 LTS independently and it does support 2 external monitors with Optimus disabled.


If optimus is enabled , ubunu , also supports only 1 external monitor and response also is very slow.


This certainly leads to conclusion that , if 2 external monitors are to be used , then Optimus must be disabled.


Optimus disabled , then both Win-10 and Linux , both  supported 2 external monitors connected to Dock.


This means , for OSX also Optimus needs to be disabled to support external monitors.


Here is intel_reg_dumper file : intel_reg_dump.txt


Please let me know , if you could help me to do necessary modification in OSX to support external monitors connected to Docking station.


Thanks in advance for your time and suggestions.




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I assume that when Optimus is disabled, only integrated HD3000 is active. In that case, it's very simple: patch the SNB frame buffer as per indicated in EmlyDinesh's HD3000 patching guide in R&D->Graphics section or in my E6320/E6220 posts on the matter:





Once you've patched the SNB framebuffer kext, use IORegistryExplorer to identify the port number associated with each DVI output of your docking station, i.e. plug the cable and check your IOReg frame buffers under the iGPU section. You may have to adjust your patch according to your findings.


I'll try and test my E6220 with an E-Port Plus (the dual-DVI model) port replicator later on.

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Dear Herve,


Thanks for your help and appreciate your willingness to help me out.I apologize for not giving you complete information.

Here is picture of OSX El Capitan as well Yast Hardware info taken from Suse Linux Leap 42.2.post-100830-0-18027400-1485993775_thumb.jpegpost-100830-0-98012900-1485993799_thumb.jpeg


This is Hardware Info taken from Yast related to Graphic.post-100830-0-59838200-1485993849_thumb.jpeg


These are taken when Optimus is not selected.


That means both different OS has taken Nvidia Graphic when Optimus is not selected.


But Linux can support 2 DVI ports , wheras OSX doesn't detect DVI and only supports Laptop LCD.


That means Intel HD3000 does not come into action when Optimus is not selected.


I tried to give you more accurate information , hope this will be useful for possible solution.


Once again , Thank you & appreciate your time.

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You don't appear to have graphics acceleration for that nVidia GPU under El Capitan...


Can't you configure your BIOS to use only the integrated HD3000 for which there's a better chance to be able to obtain dual DVI output through SNB framebuffer patching. If the DVI outputs remain driven by the iGPU of course and they're not actually wired to the dGPU...

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Since external DVI is only working when Optimus is not selected , does imply that probably HD3000 may be not configured for external monitor via Docking station or e-Port replicator.


As well Nvidia shows up in Win-10, Linux and OSX , when optimus is not selected.I am not sure , where to from here now.


Thanks for your time.

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