The situation wasn't that good just a scant 15 or so years ago. Back in the bleak days before the triumphant return of Steve Jobs to 1 Infinite Loop, Apple had a broad and confusing product line. Since DOS and Windows 3.1 were already entrenched in business worldwide, Apple knew that they had to have a way for Macs to run Microsoft operating systems in order to gain any sort of traction in the corporate world.
Edible Apple ran a wonderful retrospective yesterday that looked at Apple's DOS Compatibility Cards. These were basically PCs on a NuBus or PCI cards that were inserted into a slot in the Mac, using the Mac's power supply, floppy and hard drives, and keyboard and mouse. Sporting such amazing CPUs as the Intel 486SX running at a whopping 25 MHz clock speed, the original cards worked with the Centris 610 and Quadra 610 and were released in 1994. By the next year a second edition was released with an Intel 486DX/66, and was targeted at the PowerMac 6100 and Performa 6100.
Further research shows that there were several subsequent cards that included even faster Pentium and Cyrix 6x86 processors, were called "PC Compatibility Cards," and were designed for use in other PowerMac models. I can recall acquiring one of the Pentium-based cards and using it to try to entice our one DOS holdout department to move to Macs (they didn't).
Today's Windows compatibility is the best it has ever been on the Mac platform, and usually the only "hardware upgrade" required is to add some inexpensive RAM to the host Mac. Things might sometimes change slowly, but at least in the world of technology, the change is usually for the best.