[dcornutt]

The largest difference seen so far has really been between having one (an L3) and not having one.

There is some debate as to the marginal difference having over 1 meg of L3 makes.
My guess is...that's the least of the new architecure problems as far as performance...and that adding another meg L3 (if you could)..would not change things much at this point.

The L3 is soldered onto the MB in new macs..and on daughter card of old G4s ...so it's not "upgradeable" in and of itself.

And it does make a good difference between having one and not having one. But, I've seen no hard data about performance increases between a 1 meg L3 and a 2 meg L3..and considering the other limitations of the designs (the front side bus being 1.3gbs shared bandwidth...even though the backside is running at DDR 2.7gbs)...I would guess..it probably would not make much difference at this point between having a 2 meg or 1 meg L3. Thats the least of the worries.

Hope that helps.