They had one (4167) for the 486 too, I have no idea if it only worked with 486SX systems, or if it could work alongside a DX (but then who'd have a co-processor

They had one (4167) for the 486 too, I have no idea if it only worked with 486SX systems, or if it could work alongside a DX (but then who'd have a co-processor socket on a DX board anyway, co-processor sockets had already become scarce in the 386 period). By that era they appear to have mostly pivotted to their own 486 clones and VGA chipsets though. edit: I just realised, it could have been like the Cyrix 487S which installed as a PCB carrier that plugged into the 486DX socket, and then had a socket on the carrier for the CPU itself, alongside the 487S chip.