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Analysts: Will there be an Apple designed GPU?

Posted: 22 Feb 2013 ?? ?Print Version ?Bookmark and Share

Keywords:A-series? processors? CPU? GPU? die?

There isn't much to add except to say that Apple is serious about and making considerable investment in their design capabilities. So, regardless of the reason for the custom design, this clearly supports the hypothesis that Apple is not producing placeholders while it waits for an Intel processor.

Chipworks presented some quantitative numbers comparing the A6 and A6X, in their November 1st discussion of the A6X. With a die size of 124 mm, the A6X is 28% larger than the 96.7 mm A6.

The CPU consumes 15 mm on both parts, while the triple core GPU of the A6 weighs in at 16 mm, and the quad core GPU on the A6X comes in at 35 mm.

From the above numbers it is apparent that beyond the additional 19 mm for the GPU the A6X sports approximately 10 mm additional area. This may not seem like that much, but it is actually an area larger than the individual GPU cores.

In terms of accounting for this additional area we can again turn to Chipworks who noted that the A6X doubled the SDRAM interface width and included some new interface blocks. They also observed one fewer PLL for the A6X which freed up some mm.

So we gain some area here and use a bit less there. The question though is whether there are other differences. We will take a look at this, but in the context of the evolving A-series family. A visual interpretation of Apple's chip lineage should help.

An A-series family tree is presented below. Starting with the A4 in 2010 and ending with the A6X just a few months ago, there are now 5 members in the family. Basic information for each AP, including the device in which it was introduced, its dimensions (mm) and die size (mm2) are included. The tree has been constructed to schematically illustrate two major evolutions that have occurred within the family over the last three years. First, the original family line bifurcated into two distinct lines of APs. Second, the family went through a process "shrink" from the original 45 nm to the current 32 nm fabrication process. Each of these events will be considered in more detail.

Apple's A-series family tree

Apple's A-series family tree.

The "X" branch was introduced at the "5" generation with the A5X in March 2012. Its die size grew by 35% compared to the A5, i.e. the same generation of the other branch. At least some of this extra area was due to a doubling of GPU real estate.

The increase in graphics horsepower compared to its generational counterpart emerged with a four-fold increase in the number of pixels from the iPad2 to the iPad3.

Further evidence of the bifurcation of the A-series family came in the digital blocks outside of the CPU, GPU and GPU spine. There are 12 for the A5 and 15 for the A5X.

What does this bifurcation look like at the "6" generation of the A-series family?

As pointed out above there is again much more real estate devoted to the GPU in the A6X compared to the A6. We also know about differences in the layout, interfaces and PLLs. It is time to look at the digital blocks outside of the CPU and GPU.

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