On Tue, 23 Mar 2004 18:37:01 +0100, Thorsten Froehlich <tho### [at] trfde> 
wrote:
> In article <opr5brv9e1zjc5hb@news.povray.org> , Fredrik Eriksson
> <noo### [at] nowherecom>  wrote:
>
>> That is, in fact, the way Pentium4 processors do integer multiplication.
>
> This is plain wrong. Integers are not converted to floating-point 
> numbers.
> They simply used the same multiplier hardware.

Which, in reality, is virtually the same thing, and has the same effect:
Integer multiplies are slower than FP multiplies.
Even if the data is not actually converted, it still needs to be moved
back and forth.
Strictly speaking though, you are correct.


>> It has little to do with stupidity, and everything to do with saving 
>> space
>> on the die.
>
> While in the first Pentium 4 processors the complex integer unit and the
> floating-point unit did indeed share the multiplier hardware, this is no
> longer the case in current processors of the Pentium 4 generation.

True. An integer multiplier (along with some other goodies) was
introduced with Prescott.
Northwoods are still being sold though, and are available at the same
frequencies (and almost the same price) as Prescotts.

Nitpick: Not only the first, but also the second generation of P4s had
this "problem".


> Sharing
> the multiplier unit causes serious contention problems, and it definitely
> cannot have been the preferred solution, only one Intel had to use until 
> it could afford an even larger die.

Actually, they decreased the die size. The number of transistors was more
than doubled however.



This is getting awfully off-topic...

---
FE

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