Pentium 90? I think my dad got a pretty good deal on the 486. I think Pentiums at the time were a fortune. He may have bought it at the end of 92 I can't remember. Either way it was way better than the 286 we had before it.
edit: Just looked it up. The pentium didn't come out until 93.
Yes, the Pentium didn't come out until 93 and even then, only in 60 and 66 Mhz versions IIRC. The next tick was the release of 75, 90, and 100 Mhz models IIRC and that was in 94 with 120 Mhz and 133 Mhz following in 95. I remember, because my first PC build was in 95 with the all new Pentium 120 that I paid close to $1000 for.
As far as the 486 goes, there were 486 DX4 CPUs up to 100 Mhz (and I think AMD or someone made a 120 Mhz and/or 133 Mhz version as well), but it was very common in the early 90s to get 486 SX CPUs in the 20 to 33 Mhz range. My brother got a 25 Mhz model in 92.
My first version of Windows was one of the 3.x variations. Prior to that, I was Commodore only (Vic 20 through Amiga).