UEFI cannot be "installed" onto a board that was not designed with it. UEFI is not possible on an 840. Even if you could, it would not enable the use of 4TB drives on a RAID controller. UEFI only applies to BOOT disks (volumes, LUN's, VD's) that are larger than 2TB. UEFI is not necessary for data disks larger than 2TB. The hardware must support it. There is no programming that can change the limitations of the given hardware. The only option is to replace the controller, which may require replacing the motherboard. Measure and check the position of the mounting screws for compatibility with third-party boards. Remember that Dell servers are not intended to be upgraded with third-party hardware, so there is no reason to expect everything to line up and be compatible. If you can find a board that will fit the chassis and control panel/power connections, getting a different controller will be trivial. I'd recommend LSI.
I am a newbie here, but I have been studying the forum for days. I am determined to make (4) 4TB drives function in my Poweredge 840.  I understand that the PERC 5/i controller is not going to do the job.  My question is this:  Is there any controller card I could buy that would work with the motherboard and do this?  Is there any modification I can make to the system that would allow me to use the OEM motherboard? Just in case someone knows and is willing to share their information, I have one more questions. Can you recommend replacement equipment that will do the job?  I would at least like to use my dual core Xeon processor in an lga775 socket.  I've got the money, just not the knowledge.  I am having a terrible time finding out the maximum drive size of the various RAID cards. Can I add a UEFI to my PE 840? Thanks in advance!! - Michael    
How can I RAID 4TB drives on my PE 840?