Once upon a time …… Or at least 20+ years ago my friend Johan and I struggled with the delightful dilemma of having to much RAM in our shared computer. Johan, which at the time worked for IBM could by a blazingly fast IBM PS/2 50z at about 50% off the market price. If I remember correctly it costed 25.000 SEK with the discount. A lot of money now, even more then. So Johan asked if I would pay half and we could share the computer. We used time slicing, one would have it for one week, then bring it to the other. At that time we lived in the same building and my mother managed to get hold of a “computer desktop” with wheels which we placed the PC (sorry PS/2) on. We would go down the elevator, run through the long corridor and up the other elevator, how’s that for timesharing 
?
Johan was also able to buy extra RAM (which was very expensive then) cheap from work. If I remember correctly we had 4M RAM (yep, Megabytes, not Gigabytes) which was a lot then. DOS could only use 640K directly, the rest was fixed with extended memory stuff which I have mostly blissfully forgotten today.
We never succeeded in using all that RAM so we had to find another use for it.
Enter Virtual Disk!
Since we had an excess of RAM we could use a good program called Virtual Disk (or something similar) to create a volatile disk from some of the RAM. We created a virtual disk of 2M from our total of 4M. We could then copy programs, mostly games, onto this superfast volatile disk and run them much faster.
