cripes you're right, I had always assumed that Pentium was a big deal because it was 32-bit, and that the previous 386 was 16-bit. In the late 80s I'd heard of IBM Pcs but didn't encounter one till the pentium era.
You may be confusing the operating system with the processors. Windows 3.x and earlier were 16-bit operating systems that were run on PCs well into the 32-bit era. Windows for Workgroups 3.11 was, I believe, the first full 32-bit version of Windows. 32-bit Windows only became widespread, at least amongst consumers, with the release of Windows 95.