Jake, it is an interesting procedure they go through to make chips. We watched a video in one of my lower level engineering classes. The video was probably from the mid 90s at best, so while some of the processes to make them have changed, most has stayed the same. They were showing how they build a chip by building it up and creating the gates for current flow.
Now, how does Intel tell between a 920 and a 965 D0? I can only guess where it would happen. There is no physical difference between the two, i.e. one is not a disabled version of the other. When you have errors building the transistor stack, you could end up with a partial which could be sold at a lower cost. Kind of like how some Phenom IIs can be unlocked and others can't. The ones that can't are because part(s) of the circuit that didn't come out as they should have. Since we don't have that situation, we have to assume that when Intel went to building 1366 chips from the initial die, they were able to build 2 full and working chips initially able to become any one of 1366 chips, from Xeons to i7s.
From what I can remember from the video, there two tests after the chips get built and look as if they should work. Basically, you can build the chip and it look alright, but when you go to apply voltage, a transistor(s) doesn't work and causes the chip to not fall with in the allotted voltage specifications or not work at all. I can't remember what the two processes that the video showed, but the basic is this: one was to test for voltage while being in an oven and cooking, the other was to test to check instruction errors that they programmed the chip for in a similar environment.
I'm sure Intel has other final steps for deciding which 1366 gets labeled as a 920, 950, or 975EE. As this is a new architecture for them, and the first with an IMC, it doesn't really surprise me that it has taken this long to get it figured out. For all we know, the same thing might happen again when they go to the next stepping. Eventually, there will end up more consistency like that we have seen with the Core 2s.
