W520 won't boot to external monitor

[Hamburgler]

Hello, I have a W520 with a 4338-30 docking station. I have an external monitor plugged into the DVI on the docking station and when the laptop is docked, it does not boot to the external monitor. I have to open the laptop to log in. Once the laptop is all the way booted into windows 7, I can then view the screen on the external monitor (albeit with a lower resolution). It worked fine when I had XP.

I did go into the BIOS to change it to the external port (DVI) however, only the Thinkpad LCD is available as an option. I did update the BIOS to 1.37 to see if that would fix it, but  that did not work.

Anyone have any suggestion?

[ThorsHammer · Accepted solution]

You can thank the funky Optimus implementation on the W520.  If you set the BIOS Display graphics device to Discrete, it will do what you want.

[christopherlang]

I think you also need to turn Optimus off or there is another setting, can't recall specifically. You need to select the external device. Otherwise for what you have set seems correct it not showing the other display until you are nearly completely booted into Win 7. I am not using a dock and my external display is via the displayport connection and booting using an external display works least on my system.

[jcl777]

Thanks for the info on discrete mode.  I had same problem as the OP with a T420 and a 4338-20U.  Problem now solved!