This is older technology from the mid-1960s that refuses to die out! In the ’60s, before the advent of the PC, access to computers was expensive. As a matter of course, many users would connect to a single server-grade mainframe machine. Mainframes were built for reliability and stability, and as compared to standard PCs and server technology, mainframes contain multiple CPUs running into dozens, have thousands of GB of RAM, and high-speed hard disk subsystems that can hold terabytes of data. Mainframes have a Mean Time Between Failure (MTBF) rating of 20 years. Of late, interest in mainframes is being revived.