We've also had "RAM disks" and "RAM drives" of various kinds for 30 years or so. For example, a built-in one on a piece of hardware that holds the boot operating system, or enough operating system for the device to find the network and boot from there. And, even today, if you boot from a Windows rescue diskette, it holds more than a diskette's worth of the command line utilities and decompresses them to a RAM drive with its own drive letter. Wikipedia on Ram Drive