Macmini smbios with HD 530 & discrete gpu

Hi.

I installed sierra on this system.

CPU : i5 6600
MB : ASUS B150M-K
GPU : HD 530 (inject intel : check, ig-platform-id : 0x19120000)

I used macmini smbios. Booting with HD 530 (no discrete gpu) has no problem. When I install discrete gpu (hd 6450), it also boot but finder got some artifacts like picture.

How can I fix this?

* With nvidia gpu, boot failed after verbose screen. AGDP fix didn't work.

Well.. it's so simple. I changed discrete gpu to hd 7770 & artifacts are gone. Maybe problem with hd 6000.