Well what an interesting couple of days. Firstly an apology ... I failed to notice that Stork's MultiBeast build included "eSATA" not "SATA". As I don't use eSATA I can't comment on the need with my Sierra test drive and our MB. Now the last days. Having been on El Capitan I decided to do a clean install and use Multibeast as I had upgraded from Yosemite to get a clean reliable 10.11.6 install with the latest drivers rather than the original pre Multibeast build using the starting Clover package and composite kext installer. What a mistake. Despite having carbon copy clone and a time machine backup I had forgotten that I did a migrate from a smaller drive to a larger one and had no EFI clover setup on the 500Gb Samsung EVO 850 SSD that I used for the El Capitan main drive. Having worked that out and starting with a clean install, I re-partitioned the Samsung 850. Now the issue is ... MultiBeast WILL not install anything on this drive. Neither would a Clover bootloader install only. I've been through every incarnation of attempts, confirm the right MultiBeast versions, mounted EFI before install attempts, etc. In the end, the only way around the issue is to continue was to boot off USB install, then use the original "smaller" 120 Gb Samsung 840 drive and I did a migration to get all the info onto the 850 and finally I have a working El Capitan system. I have read everything I can regarding this and was wondering if anyone here can point me in the right direction to get the Clover bootloader onto the EFI partition of the 500 Gb EVO 850 drive preferably with the latest El Capitan Multibeast. The only advantage is I did upgrade to the modified F12j BIOS from Tweaktowns and have found it to be much better in many aspects including boot screens in full res .. boot speeds etc. Feeling very stupid and extremely frustrated ... Edit - Got it going again. Copied original EFI over from backup El Capitan to clean rebuild. Now to get Imessage working again.