First A7 Die Shot
Below are A7 (28nm), then A6 (32nm), then Bay Trail (22nm) for comparison. I did some quick measurements in mspaint, for those who are interested. All sizes are normalized to 22nm. Conversion is 0.7^2 for 32nm-->22nm, and 0.9^2 for 32nm-->28nm. The CPU includes all the cores and all the cache, while the GPU includes all of the regular arrays that can be seen in the die shot, but probably misses fixed function media, etc, which are likely in other areas around the primary graphics arrays.
Die size of Bay Trail is in the datasheet (102mm2), last page, if you zoom in on coordinates C1 (9.723mm) and C2 (10.477mm).
Die Size CPU Size Normalized GPU Size Normalized
A7 102mm2 17.8mm2 10.77mm2 23.2mm2 14.0mm2
A6 97mm2 15.2mm2 7.45mm2 20.4mm2 10.0mm2
Bay Trail 102mm2 17.1mm2 17.10mm2 18.6mm2 18.6mm2
- Given that Bay Trail has 2x as many cores, I can understand how normalized CPU area ended up 60% larger than A7. Still, with performance less than 60% faster, Apple clearly has better perf/area efficiency.
- The normalized GPU area does suggest that Bay Trail's graphics are also less efficient, but part of that does include the significant overhead to enable DX11 (and from what I recall, Imagination 6-series does not). This is important under Windows, but does not currently get used under iOS. However, Android will eventually support OpenGL-ES 3.0, which will probably use the same functional transistors, and so Intel will likely be able to support those features, and overall improved graphics rendering quality.
Overall, it does appear that Apple achieved both a very high performance design, as well as a fairly area efficient design. You can also see that the normalized growth over A6 (44% on CPU and 40% on GPU) is pretty nominal, given the generational performance increase. Performance per area has gone up dramatically, and given the half-process shrink to 28nm, was nearly washed out.
Intel will need to step up their game. While I think Bay Trail will still win in the Android and Windows ecosystems, I'm hoping the 14nm generation products get the improvements in density needed to be the market leader.