yes it is true. my device z1 and my friend device is z1, too. we bought them almost same date. both we are using 1409 image verison. we used same config but he made oc to 1000 mhz but i can not. think about how come it is possible. this is strange.
This is called "silicon lottery". Google it.
yes i read it thanks. but it is little bit different. i think manufacturer limited some machines by bios. and then they announced zig1 plus. they sold more.