I have been experimenting with EGPUs over the last six months or so, but it seems possible that EGPUs and the x220 do not agree on something, despite that I have seen many success stories online.
First I bought a PE4C-EC100C base to use with a hd6900 and a regular ATX power supply. This worked great: I was quickly able to install drivers and use the video card as I wanted. However, in the following weeks, after connecting and disconnecting this device a few times. I started getting an issue where the laptop would not power on. I would press the power button, all of the leds would come on for about two seconds, then turn off for three seconds, and this would cycle forever. Sometimes I managed to fix it by removing the battery or using a different power adapter, but the problem normally came back a day after using the EGPU setup, so I stopped using it. A little after that the problem happened and I could not end up fixing it, so I had to purchase another mainboard from ebay, which is what I am using now.
Because I had read and seen so many other success stories using the x220 and no mention of this issue, I thought that the EGPU adapter could be at fault, so I bought an updated model which was recommended to me over IRC: The PE4L-EC060A. Again, when I started using it, it functioned great and gave no obvious crashes or issues, but now today again I have symptoms of the power issue. The power would not fully come on as described before, and I had to remove the battery to get it to turn on again. I am, of course, afraid to use the egpu again, when through it is serviceable to me. (It allows me to use more than two monitors, which is not possible using the intel GPU)
When using the EGPU, I always shut down the computer, then plugged or unplugged the expresscard connector, then turned it back on. When I did this, it would often power on for a second, shut down again, and then power on correctly. This is unlike the error I have where it just keeps cycling.
So now I want to have this thread documented incase anyone else has the same issue, to know they are not alone. I am also awaiting any suggestions that the community may have to allow safe operation of the EGPU, which provides great benefits to me.
bluefruit from thinkpad forums has some additional information to add, but suggests that I ask my question here where there may be more EGPU users:
Bios version 1.4
Bios setting > 'pci express speed' : 'generation 1'
i7 16gb ram (I have not had any '100% cpu' issues described elsewhere using 16gb)
PE4L-EC060A with 300W ATX power supply and AMD hd6900 ; using the expresscard connector
Please let me know any other required information.
Thank you for reading.