/dev/fb* no such file or directory

Hello, my system is Ubuntu 1604, and i have three graphics cards ( one card from motherboard ).

After system boot up, i don’t found /dev/fb*, so i add command “fb:on vga= 0x317” in grub, then i get /dev/fb0,

But only this, other words, my two graphics card is not create fb*.

what? should i do?