wrldwzrd89 said:
That disproves the cooling hypothesis....so there's GOT to be a reason why Apple's going with 2.3 GHz PPC G5s for the XServes...I just can't determine what that reason would be.
A couple of possibilities:
1. The *existing* XServe heat sinks and cooling system can handle the chip at 2.3 GHz, but not the extra heat from running at 2.5 GHz. The chips at 2.3 could be stuck in with little effort, but 2.5 would have required re-engineering the cooling system.
2. Apple didn't have 2200 chips that would run at 2.5 GHz, and didn't want to shut down sales of the PM 2.5 in order to supply VAtech. They did, however, have a bunch of chips that wouldn't run at 2.5 GHz but which were OK at 2.3 - viola!
Note that there isn't a "2.5 GHz" manufacturing line and a "2.0 GHz" manufacturing line. There's one line, and all the different speed chips start out identically.
After the chips are manufactured, they are tested. Due to differences at the atomic level between chips from the same wafer, different chips from the same wafer will have different maximum speeds. You could easily have a 1.6 GHz chip come from right beside a 2.5 GHz chip on the same wafer.
Typically, you'll find that chips that will run at super-fast speeds are rare compared to slower chips.
Since Apple is currently has no product between 2.0 and 2.5 GHz, one can assume that there are a bunch of chips around that will run faster than 2.0 GHz, but won't quite make it to 2.5 GHz.
(IBM is only selling 1.6 GHz systems, although the Spanish cluster was described as using 2.2 GHz CPUs.)
