Cant see BIOS after resetting CMOS however OSX boots fine

Hi there knowledgeable ones. I need help!

I've been battling this for over a day now and i'm pulling my hair out. For reasons I'd rather not go into I reset the CMOS to reset the Bios settings. My build should usually run on optimised defaults but now I can't see the bios and Clover bootloader when booting - I can however get to OSX. After waiting a minute or so OSX appears on screen.

It's like my GPU is not being recognised by the bios or bootloader. What's more strange is that if I clear CMOS I sometimes can get the BIOS to post and jump into the BIOS settings - but once i've booted OSX I will have lost the BIOS posts completely on subsequent reboots.

I'm running off my DisplayPort on my AMD 290x GPU (which i always have done) and my mobo is a Gigabyte Z77n_WIFI. I'm running El Capitan (10.11.6).

I've tried to run off the HDMI on the GPU with mixed issues too.