I'm having a Mac Pro 1,1 (firmware upgrade to 2,1) as this Mac is not native supporting El Cap 64bit Boot, the boot.efi files need to be replaced with costum made files in order to boot into the OS.I'm about to do something similar, but I didn't know I had to do anything with the Boot.efi files. What needs to be done and why?
I'm confused-- what's going on in the first half of your post? Are there more than 2 x16 slots?Not really time for benchmarks but i think i can hold up with "custom" by now....
Mac Pro 4,1
256GB SM951 (via Lycom in case mounted) + 480GB SSD on SATA bay
4 port x4 USB 3.0 card
R9 280X, flashed
R9 270X, unflashed
2 x16 cards in the DVD bay, expanded from internal unused mini PCIe - Full album: https://imgur.com/a/sK0Z0
Using slot 3 as x4 even though it is covered by a 2 slot GPU - by PCIe extension cable and taping the NGFF/M.2 adapter in the case - Full album: https://imgur.com/a/81NVk
And the current setup: