Image Source: Chipworks (left side) and UBM Techinsights (right side)
The use of reverse engineering (RE) as a marketing tool can have its ups and downs, including a fair dose of unpredictability. On the positive side RE can provide some very quick gee-whiz impact, with plenty of big, neat equipment. It can also provide a glimpse into a world not often visited by the “average” person. A world that can be presented in greater detail than the typical comparisons to the width of a human hair. On the negative side RE information can be difficult to understand by an audience not familiar with it. As far as unpredictability goes it still has a component of an inexact science that can rear its head, particularly when rushed. All in all RE is not familiar with the spotlight. What does all this mean for the initial A6 coverage?
First, a bit of background
An integrated circuit or die is, at its most basic, a piece of silicon with active circuit elements, mostly transistors, on one surface. These circuit elements are wired together with up to 9 layers of metal traces or lines built up “above” the circuit elements. Insulating layers are formed between and around all the conductive elements, including the silicon die and the metal layers. From here areas of the die are electrically connected to leads in the package. In a final step the die and internal connections within the package are entombed in resin, giving the standard black package seen on circuit boards. So if you want to see how the circuit elements are arranged on the die you have to remove the die from the package and then remove all of the metal and intermediate layers of insulation.
Now on to the A6
With the public debut of the iPhone on September 21st came the the race to look at the A6 die. The two big RE houses were entered along with their respective publication partners. Who won the race? The first image I saw was this one from UBM Techinsights. Chipworks came out with their own image shortly after. In the end UBM was first, but did they win the race? I can’t say they did. The image was of poor quality because the die was not fully delayered. Without knowledge of the RE process (i.e. the majority of the audience) it is easy to be confused by the image. To this end the CPU and GPU blocks are obscured by the remaining insulation or dielectric. There was a rather protracted discussion about this “green moss” in the comments to this arstechnica article. On the other hand the Chipworks photo came out a few days later. It was pristine. Everything was in focus and the die was free of unwanted residue. To the trained eye there is a lot of detail there.
In the end RE information seems to be more prevalent today. This is at least partially through its wider use as a marketing tool. The kicker is that in the absence of an explanation of RE the information can be lost on the audience. Once the the information is placed in context, though, a whole new world unfolds.