Ricardo B (ricardo.b.delete@this.xxxxx.xx) on May 15, 2013 4:15 am wrote:
> Doug S (foo.delete@this.bar.bar) on May 14, 2013 5:51 pm wrote:
>
> > How much more die area does adding another core add these days? More than 5%, but not a whole lot
>
> An Ivy Bridge core is 12mm², or 8% of the area of a 4C/GT2/8MB L3 chip.
>
Sorry, I meant 5% of a CORE not the whole die! So at best the saving you would make on removing from a quad core only buys you 1/5 of a new core - not really worth it if you ask me...

> > cases, along with SMT, which addresses the "niche" of servers. It is nice that it helps in certain cases
> > on desktops as well, but desktops were not the target for SMT. Even if it never helped on desktops and
>
> Well, Atom was not aimed for servers and it had SMT.
> And trust me, it helps!
>
To be fair, that is because Atom was a rather poor in-order design. SMT just made it perform slightly less badly.

> > actually cost a few percentage points it would still be in the desktop core - it would just be fused off.
>
> Which it is, for quite a lot of models.
> The mainstream Sandy/Ivy Bridge models are 2C/4T and 4C/4T.
> There are a few 1C/1T and 2C/2T models and the very expensive 4C/8T (and 6C/12T) models.
>
>
>
Well that's the point. SMT lets you have a 4T chip with the performance of ~ x3 of a core with only half the die area. That lets you get a lot more cores out the same wafer or to reclaim defective 4C die by fusing off the defective cores. Either way that keep costs down and is good for the low end. Especially since a 2C/4T Sandybridge performs at least as well as a similar clockspeed 4C (2 module) Piledriver is most desktop workloads.