The 486SX and 486DX are identical chips (access memory the same way, 8K
internal cache, etc.) except for the fact that the 486SX is "crippled".

Explanation: The math co-processor on the 486SX is disabled.

That's it. If you do work that requires a lot of number crunching, then you'll
see a noticeable difference in speed (if the programs use the math
co-processor). Otherwise, the difference is minimal. Graphics will be
slightly slower.

There was a big fuss over the disabled FPU when the 486SX was released. Some
people are still upset about it. The 486SX is still faster than most 386's,
but the big advantage of the 486DX is the integrated math co-processor.
Without the FPU, an i486 is nothing more than a more efficient 386 with an
internal cache.

FYI, the AMD 386-40 MHz chip is faster than a 486SX chip.

I think you're correct!!