The Math Coprocessor
Gamers who spent years playing Doom and its derivatives on a 486 computer were probably in shock when id Software's Quake wouldn't run on systems with NexGen and 486sx chips. Specifically, the pre-release "demo," called qtest1, was released in early 1996 to see how the game would run on various systems. id said that it was possible to run the test using an emulator (Q87 or the WMEMU387 in DJGPP). However, the frames would run extremely slowly. Evidently, the game needed floating-point math support, and a math coprocessor was the ticket.
In this case, the chip was used to offload the extra math calculations the 486 couldn't handle on its own. Of course, meatier processors and GPUs came along to help out with the rendering, however qtest1 and its math coprocessor requirement were two signs that PC gaming was about to take on a more serious tone on the hardware front.