Help Installing Yosemite on a Dell Inspiron 530S, AMD r7 240

[Chiu Meister]

So I have a intel core 2 duo e8200 4GB RAm AMD R7 240 graphics on a dell inspiron 530s.

And i want to install yosemite on it, i am planning to install it on a seperate hdd and whenever i want to boot in mac i can simply use the usb to boot and i want to keep the current bootloader the same. 

However the issue is that my motherboard's bios does not have an option for ahci, but when i boot into the usb installer i can format my hdds and then instlal mac os on it, but im afraid because i don;t have ahci it won't work.

SO can someone help me, i have the latest bios installed.