You can slightly overclock your Gen3 by typing the following command :
setxenv_mtd.sh 0 -b x.pll.1.pll 0x0100003b

The frequency will change from 715 MHz to 810 MHz at the next reboot.
3B corresponds to the value of the PLL frequency multiplier core (27 MHz)
(HEXcode + 1) * 27 / CPU_Mux = (3B + 1) * 27 / 2 = 810 MHz

Do not exceed the value 3B. Beyond that, the boot can not read the Nand and your Gen3 will be bricked. But 3B value is perfectly secure.

I continue to seek ways to exceed 810MHz…