487 is a 486dx/dlc-compatible (FPU enabled) replacement for the 486sx/slc (FPU disabled).
There are actually several flavors of x87 ISA: 8087, 80287, and 80387. Every 386+ chip supports the 387 ISA. The 287 is almost the same as the 387. The 8087 is almost a strict subset with some differences. There were also Weitek math coprocessors that were entirely different. The IIT 3C87 was an odd bird that supported the 387 ISA and some other instructions.
There are actually several flavors of x87 ISA: 8087, 80287, and 80387. Every 386+ chip supports the 387 ISA. The 287 is almost the same as the 387. The 8087 is almost a strict subset with some differences. There were also Weitek math coprocessors that were entirely different. The IIT 3C87 was an odd bird that supported the 387 ISA and some other instructions.