CPU Performance  Like the A6, the 4th generation iPad's A6X
integrates two custom designed Apple Swift CPU cores that
implement the ARMv7 instruction set. The two cores share a 1MB
L2 cache, just like they do in the iPhone 5's A6. I spent a lot
of time characterizing the architecture and performance of Swift
in our iPhone 5 review, so I won't go over a lot of that here.
What I will say is that Swift manages to be the best balance of
performance and power efficiency in an ARM based CPU core
available today. Swift looks a lot like Apple's take on
Qualcomm's Krait core. It's not a Cortex A15 competitor from a
performance standpoint, but likely a more power efficient
design.  Unlike what we saw in the previous iPads, the A6X only
boasts a marginal increase in max clock speed (~7%) over the A6.
The two Swift cores can run at up to 1.4GHz in the A6X compared
to 1.3GHz in the A6.  Apple iPhone/iPad CPU Clock Comparison  
iPhone iPad iPad Frequency Advantage Apple A4 Generation 800MHz
1.0GHz 25% Apple A5 Generation 8