Thorsten Froehlich <tho### [at] trfde> wrote:
> Warp wrote:
> > Thorsten Froehlich <tho### [at] trfde> wrote:
> >> For two decades now the CPU and FPU have been the same thing on x86. It is 
> >> not like they are two different processors. They are *one* processor. The 
> >> terminology is just a leftover from times when the logic we nowadays call 
> >> FPU did not fit on the same die as the integer unit called CPU back then.
> > 
> >   That doesn't matter.

> When did I say it does? You asserted it would:

> > The CPU part does not stop if the FPU is doing
> > something (the only situation where the CPU will wait for the FPU is
> > when it tries to retrieve some value from it).

> "at least in theory, have the FPU calculating your operation while the CPU 
> does other (non-FPU) operations at the same time. I don't know if any 
> compiler is able to opimize like this, though."

> I am asserting that (both of) your statements are incorrect because you 
> continue to view the FPU as a separate entity from the CPU in your 
> statements. What you refer to as CPU is the combination of ALU and LSU. That 
> is not the whole CPU. The FPU is just one other component of the CPU, it is 
> in no way distinct, especially not in x86 processors.

> In fact, Intel's "Core" architecture fuses the ALU and FPU like no other CPU 
> design currently around. Go look for a Core i7 (Nehalem) block diagram in 
> the IDF videos on the Intel site, or look at i.e. this redrawn one: 
> <http://pc.watch.impress.co.jp/docs/2008/0403/kaigai_nehalem.pdf>

> Notice something? - Where is your FPU, where is your "CPU"? There are six 
> separate execution units, each with some unique and some common features...

  OMG. You blame me for nitpicking about semantics, and now you are doing
that exact same thing yourself.

  I never said the "FPU" would be a separate piece of circuitry from the CPU.
When I say "FPU" I mean, rather obviously, "the part of the processor which
performs the floating point calculations". It doesn't matter how it's
physically distributed inside the processor, I was talking about its
behavior.

-- 
                                                          - Warp

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