Though the A6X still runs two ARM Cortex-A15 cores with a heavily customized, Apple’s own ARMv7 based processor design (called Swift), the company has improved graphics performance compared to the A6′s three PowerVR-based GPU cores by moving to a newer GPU core: the PowerVR SGX 554 from UK’s fabless semiconductor maker Imagination Technologies, where Apple has an ownership stake…
AnandTech analyzed benchamrks performed by Kishonti Informatics and concluded that Imagination Technologies’ quad-core PowerVR SGX 554MP4 graphics powers the A6X package, itself fabbed on Samsung’s 32-nanometer process.
The A5X package found inside the original and now phased-out iPad 3 model had two ARM Cortex A9 cores running at 1GHz paired with four PowerVR SGX 543 cores running at 250MHz.
The A6X retains the 128-bit wide memory interface of the A5X (and it keeps the memory controller interface adjacent to the GPU cores and not the CPU cores as is the case in the A5/A6). It also integrates two of Apple’s new Swift cores running at up to 1.4GHz (a slight increase from the 1.3GHz cores in the iPhone 5′s A6). The big news today is what happens on the GPU side.
Imagination provides little data about the 554 but Chipworks was able to determine that “each GPU core is sub-divided into 9 sub-cores: 2 sets of 4 identical sub-cores plus a central core”.
Because of this doubling of the per-core count (two sets of four identical sub-cores plus a central core) and the increase in clock frequency, the A6X fares substantially better in GLBenchmark than its A5X counterpart, fulfilling Apple’s “twice as much” performance claim.