Did the Streaming SIMD Extensions replace x87 instruction set?

Question

I know that the SSEs are an alternative to the x87 floating point instruction, but is the x87 FPU still implemented in modern CPUs like Ivy-Bridge or Haswell?

Did SSEs replace the x87 instruction set?

Answer 1

The x87 FPU is still available. It may or may not use the same hardware as the SSE units, and it may be faster or may be slower, but your CPU will still understand the x87 instructions.

So no, it is not a clean replacement (there are also things you could do in x87 which are not supported in the SSE instruction set)

But consider that if they suddenly removed support for the x87 instructions, every program which relied on it would suddenly stop working.

Ouch.

Answer 2

As far as I know, there is still no SSE replacement for the x87 remainder instructions FPREM and FPREM1, which are typically used to implement C functions like fmod, remainder and remquo. So it will still be used for a while yet.