> Separate FP registers - This looks to have started when FPUs were optional and/or physically separate, but that's no longer the case.
Using a separate register set for FP is not just about making floats optional.
It also allows to better isolate the float and int units and to build a more efficient micro-architecture.
For example: using a single physical register bank for floats and integers would be expensive (as the size of the register bank grows quadratically with the number of read/write ports), therefore using separate physical register bank for float and integer is more efficient.
Using a separate register set for FP is not just about making floats optional. It also allows to better isolate the float and int units and to build a more efficient micro-architecture.
For example: using a single physical register bank for floats and integers would be expensive (as the size of the register bank grows quadratically with the number of read/write ports), therefore using separate physical register bank for float and integer is more efficient.