I am sure that there are many many people out there who still use Snow Leopard because they have programs that cannot be used otherwise. I have recently partitioned a drive, Put snow leopard in half of it and put El Capitan in the other half. I can easily, by going to system preferences and then startup disk and then choose snow leopard while I am in El Capitan. While in Snow Leopard I go to system preferences and then startup disk and find that the only way to get to El Capitan is to choose network. This usually does work but is very slow and discouraging. Has anyone come up with an app to fix this? Or has Apple even considered fixing this?