The 486sx had a 16 bit external bus interface so it could work with 386 chipsets. The DX processors had a full 32 bit bus and correspondingly better throughput. The 486 never included an integrated FPU, you had to add a separate co-processor for that. I could go on about clock multipliers and base frequencies but I'll spare you.
Exactly. I got scammed on my first PC when they sold me a 486 for the price of a 386. It was too good to be true. I later learned that the 486 was an SLC. Per say, a 386 with some internal cache from Cyrix (https://en.wikipedia.org/wiki/Cyrix_Cx486SLC).
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.
You're wrong. The 486SX had a 32-bit bus, just like the DX version. The difference between them is that the DX had an integrated FPU while the SX had it disabled and you had to add a separate 487 co-processor.
The 486DX had an FPU. It was the 486SX that lacked it. The "FPU" upgrade for a 486SX was a entire special version of the 486DX that disabled the original 486SX entirely.
