In my case it does not boot from eMMC neither with SW4 set to 1 nor 0.
edit: I ‘fixed’ this by changing root to mmcblk1 on my SD boot partition. So it boots from SD and switches root to eMMC. It is a waste of SD card though
I used Win32DISK (flashing back with Phoenix Card-v4.1 burning software) to write the decompressed BPI W2 Android image file install.img to the 8G SD card, then plugged it into the BPI W2 SD card slot, the SW4 switch dialed to a position, plugged in the power indicator light, pressed the POWER button did not respond, and the HDMI output port did not output. (my board used the SD card to start the Ubuntu system). Who knows what the reason is?