[Repost] Apple surprises with A8X GPU, uses exclusive ‘semi-custom’ 8 cluster design

RedRound2 · November 12, 2014

The other LTT post: http://linustechtips.com/main/topic/249152-apple-can-actually-make-an-incredible-gpu/

New chip analysis of the A8X powering the iPad Air 2 has revealed that it is even more powerful than it initially appeared.

The chip uses a unique 8 cluster design. AnandTech describes the discovery as “even better than I thought”. Although the customizations are limited, this represents a big step for the company as it is now dabbling in both custom CPU and GPU engineering, even if the leap over generally-available components in this instance is small.

Effectively, Apple has engineered a way to stick two Imagination GX6450 PowerVR chips on the same die. A die shot sourced by AnandTech confirmed this theory, although the site is unable to publish the image. Shown above is a mockup of what is going on internally.

While Apple licenses PowerVR GPU cores, not unlike their ARM IP license they are free to modify the Imagination designs to fit their needs, resulting in an unusual semi-custom aspect to their designs (and explaining what Apple has been doing with so many GPU engineers over the last couple of years). In this case it appears that Apple has taken the GX6450 design and created a new design from it, culminating in an 8 cluster Series6XT design. Officially this design has no public designation – while it’s based on an Imagination design it is not an official Imagination design, and of course Apple doesn’t reveal codenames – but for the sake of simplicity we are calling it the GXA6850.

Apple’s willingness to change even this is a strong indicator that it will be even more aggressive with GPU designs in future Apple SOC’s. When the A8X was first revealed, it surprised with a triple-core CPU design and 2GB of RAM. Combined, the tablet represents a huge leap in performance over its predecessor.

In fact, the performance improvements are disproportionate to the hardware leading some speculation that the company has upcoming software enhancements to truly take advantage of the compute beefiness. Apple has been testing a split-screen multitasking system for the iPad, which would certainly do just that.

Source: http://9to5mac.com/2014/11/12/apple-a8x-gpu-8-cluster/