|Launched||October 16, 2014|
|Discontinued||March 21, 2017|
|Designed by||Apple Inc.|
|Max. CPU clock rate||1.5 GHz|
|L1 cache||Per core: 64 KB instruction + 64 KB data|
|L2 cache||2 MB shared|
|L3 cache||4 MB|
|Architecture and classification|
|Technology node||20 nm|
|Instruction set||ARMv8-A: A64, A32, T32|
|GPU(s)||PowerVR Series6XT GXA6850 (8 cores)|
|Products, models, variants|
The Apple A8X is a 64-bit ARM-based system on a chip (SoC) designed by Apple Inc. and manufactured by TSMC. It first appeared in the iPad Air 2, which was announced on October 16, 2014. It is a variant of the A8 inside the iPhone 6 family of smartphones and Apple states that it has 40% more CPU performance and 2.5 times the graphics performance of its predecessor, the Apple A7.
The A8X has three cores clocked at 1.5 GHz, a more powerful GPU compared to the A8 and it contains 3 billion transistors. With an extra 100 MHz and an additional core, the A8X performs around 13% better on single threaded and 55% better on multithreaded operations than the A8 inside the iPhone 6 and iPhone 6 Plus.
Further comparison to the A8 shows that the A8X uses a metal heat spreader, which the A8 does not, and it doesn't use the package on package configuration with included RAM which the A8 does. This is similar to how the older "X" variants, the A5X and A6X, were designed. Instead the A8X in the iPad Air 2 uses an external 2 GB RAM module.
In a first for Apple, the A8X is reported to have a semi-custom GPU. The A8X uses an 8-cluster GPU based on Imagination Technologies PowerVR Series 6XT architecture. Officially, the largest implementation of Rogue is a 6-cluster design, indicating that Apple has made customizations to the design in order to provide higher performance. This GPU is referred to as the GXA6850, with the "A" denoting the Apple customization.
The support of Codecs by decoding and encoding is available only for JPEG. H264, VP-1 and AVC are available for decoding. HEVC 265 (8/10bit), VP8, VP9, AV1 are not supported by hardware. 
The A8X's branch predictor has been claimed to infringe on a 1998 patent. On October 14, 2015, a district judge found Apple guilty of infringing U.S. patent US 5781752 , "Table based data speculation circuit for parallel processing computer", on the Apple A7 and A8 processors. The patent is owned by Wisconsin Alumni Research Foundation (WARF), a firm affiliated with the University of Wisconsin. On July 24, 2017, Apple was ordered to pay WARF $506 million for patent infringement. Apple filed an appellate brief on October 26, 2017 with the U.S. Court of Appeals for the Federal Circuit, that argued that Apple did not infringe on the patent owned by the Wisconsin Alumni Research Foundation. On September 28, 2018, the ruling was overturned on appeal and the award thrown out by the U.S. Federal Circuit Court of Appeals. The patent expired in December 2016.
Products that include the Apple A8X
- TSMC reportedly lands CPU orders for Apple next-generation iPad
- "iPad Air 2 Teardown". iFixit. October 22, 2014. Retrieved October 22, 2014.
- iPad Air 2 Benchmark Points to A8X Chip With Triple-Core 1.5 GHz CPU, 2 GB RAM
- "Apple A8X's GPU - GXA6850, Even Better Than I Thought". Anandtech. November 11, 2014. Retrieved November 12, 2014.
- The Samsung Exynos 7420 Deep Dive - Inside A Modern 14nm SoC
- "Imagination PowerVR GXA6850 - NotebookCheck.net Tech". NotebookCheck.net. November 26, 2014. Retrieved November 26, 2014.
- "Apple Introduces iPad Air 2—The Thinnest, Most Powerful iPad Ever" (Press release). Apple. October 16, 2014. Retrieved October 16, 2014.
- "iPad Air 2 - Performance". Apple. October 16, 2014. Retrieved October 16, 2014.
- Latest iPad Air 2 component leak shows A8X chip & 2GB RAM
- "A8X's GPU - Even Better Than I Thought". Anandtech. November 11, 2014. Retrieved September 3, 2015.
- "Apple A8X vs. Apple A8 - Benchmark, Test und Technische Daten".
- Chirgwin, Richard (February 4, 2014). "Cupertino copied processor pipelining claims Wisconsin U". www.theregister.co.uk. The Register. Retrieved February 3, 2014.
- Joe Mullin (October 14, 2015). "Apple faces $862M patent damage claim from University of Wisconsin". Ars Technica. Retrieved October 14, 2015.
- Wolfe, Jan (October 26, 2017). "Apple urges appeals court to toss $506 million patent loss to WARF". Reuters. Retrieved February 22, 2018.
- Stempel, Jonathan (September 28, 2018). "Apple wins reversal in University of Wisconsin patent lawsuit". Reuters. Retrieved November 17, 2018.
- Wolfe, Jan (July 25, 2017). "Apple ordered to pay $506 million to university in patent dispute". Reuters. Retrieved July 26, 2017.