FYI: Putting the original HDD back in a PS4 does not erase it.

I'm upgrading from my old Glacier White PS4 to the Glacier White PS4 Pro. Before getting rid of my PS4 I wanted to pull the upgraded HDD out and put the original back in.

I've heard that, unlike the PS3, putting a new HDD in the PS4 makes the original drive not work. That's not necessarily true. When I started up the PS4 with the old HDD reinstalled it was right back where it was when I shutdown to do the swap. PT even works.

The only problem I could foresee is system software version differences between when the drive was removed and when you put it back in. But I only put a bigger HDD in recently so I don't know what issues that might cause. Maybe you just need the system software on a USB drive to update it.

But the act of setting up a new HDD does not immediately invalidate the old one.