Deducing details about Apple’s A6X processor (original) (raw)

As usual, Apple didn't share many specifics about its new A6 "Extreme" (A6X) processor, which powers the fourth-generation iPad. However, by looking at Apple's claims that it's "twice as fast" as the A5X-powered third-gen iPad, it may be possible to deduce what's inside.

According to Apple, the A6X processor "delivers up to twice the CPU and graphics performance of the A5X chip." In other words, the dual-core CPU can process data twice as fast as the dual-core 1GHz, Cortex A9-based A5X. It can also churn through OpenGL triangles and textures at twice the rate of the PowerVR SGX543MP4 in the A5X. So how did Apple do that?

Looking at CPU power for the moment, we already know that Apple designed a custom ARM-based core for the A6. Running at 1.2GHz in the iPhone 5, two A6 cores run twice as fast as two 800MHz A5 cores in an iPhone 4S.

However, the A5X in the third-gen iPad was clocked at 1GHz. That means Apple is clocking the A6X higher yet. Given that architectural improvements account for some of the speed increase, Apple only had to clock the iPhone 5 at 150 percent to achieve double the compute performance of the iPhone 4S. With this in mind, we believe Apple is clocking the A6X's CPU cores at 1.5GHz.

Examining the GPU is slightly different. Apple already jammed four SGX543 GPU cores into the A5X in order to achieve performance parity with the two SGX543 GPU cores in the A5 chip that powers the iPad 2. The extra GPUs were needed just to keep up with the 2048×1532 pixel Retina display, so these did not offer any graphics performance improvement. However, Apple says that the A6X pumps pixels twice as fast.