You are thinking of the 386. You perfectly describe the situation on the 386 not the 486. The 386SX had a 16 bit external bus interface so it could work with 2

You are thinking of the 386. You perfectly describe the situation on the 386 not the 486. The 386SX had a 16 bit external bus interface so it could work with 286 chipsets. The DX processors had a full 32 bit bus and correspondingly better throughput. The 386 never included an integrated FPU, you had to add a separate co-processor for that.