mobile HD4600 Dual HDMI 4k and internal 1080P flickering in intenal monitor

An old Laptop MSI GE60 i5-4210H with iGPU HD4600

Os is Big Sur 11.3

What i want is use 4K@30Hz and internal 1080P display, but default only 2560x1440@60Hz and 1080P

i have changed DVMT (pre-allocated memory for iGPU) to 128M from UEFI shell

when my OC config.plist add this

framebuffer-fbmem 00000003 (48M)

framebuffer-stolenmem 00000003 (48M)

framebuffer-unifiedmem 000000C0 (3GB)

framebuffer-con1-alldata 03061200 00080000 06000000

My AAPL is 0A260006

external monitor display in 4K@30Hz but internal display flickering always

i found when flickering internal display only about @ 30Hz

When i dragged some window in desktop, flickering stopped and in FrameMeter i found the animation was about 60Hz

So who can tell me why this happend?

Help.

Thanks a lot.