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Apple A6X
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 The A6X chip used in the fourth-generation iPad | |
| General information | |
|---|---|
| Launched | November 2, 2012 |
| Discontinued | October 16, 2014 |
| Designed by | Apple Inc. |
| Common manufacturer | |
| Product code | S5L8955X |
| Performance | |
| Max. CPU clock rate | 1.4 GHz[1] |
| Physical specifications | |
| Cores |
|
| GPU | PowerVR SGX554MP4 (quad-core)[1] |
| Cache | |
| L1 cache | 32 KB instruction + 32 KB data[2] |
| L2 cache | 1 MB[3] |
| Architecture and classification | |
| Application | Mobile |
| Technology node | 32 nm.[4] |
| Microarchitecture | Swift[1] |
| Instruction set | ARMv7-A:[1] ARM, Thumb-2 with "armv7s" extensions (integer division, VFPv4, Advanced SIMDv2)[5] |
| Products, models, variants | |
| Variant | |
| History | |
| Predecessor | Apple A5X |
| Successor | Apple A7 (APL5698 variant) |
The Apple A6X is a 32-bit system-on-a-chip (SoC) designed by Apple Inc., part of the Apple silicon series. It was introduced with and only used in the 4th generation iPad, on October 23, 2012. It is a high-performance variant of the Apple A6 and the last 32-bit chip Apple used on an iOS device before Apple switched to 64-bit. Apple claims the A6X has twice the CPU performance and up to twice the graphics performance of its predecessor, the Apple A5X.[6] Software updates for the 4th generation iPad ended in 2019 with the release of iOS 10.3.4 for cellular models, thus ceasing support for this chip as it was discontinued with the release of iOS 11 in 2017.
Design
[edit]The A6X features a 1.4 GHz custom Apple-designed ARMv7-A architecture based dual-core CPU called Swift,[1] introduced in the Apple A6.[7] It includes an integrated quad-core PowerVR SGX554MP4 graphics processing unit (GPU)[1] running at 300 MHz[citation needed] and a quad-channel memory subsystem.[1] The memory subsystem supports LPDDR2-1066 DRAM, increasing the theoretical memory bandwidth to 17 GB/s.[3]
Unlike the A6, but similar to the A5X, the A6X is covered with a metal heat spreader, includes no RAM, and is not a package-on-package (PoP) assembly. The A6X is manufactured by Samsung on a High-κ metal gate (HKMG) 32 nm process. It has a die with an area of 123 mm2, 30% larger than the A6.[4]
Products that include the Apple A6X
[edit]See also
[edit]- Apple silicon, the range of ARM-based processors designed by Apple.
- Apple A6
References
[edit]- ^ a b c d e f g h Lal Shimpi, Anand (November 2, 2012). "iPad 4 GPU Performance Analyzed: PowerVR SGX 554MP4 Under the Hood". AnandTech. Archived from the original on September 22, 2013. Retrieved September 16, 2013.
- ^ "iPad (4th generation)". Geekbench. September 12, 2013. Archived from the original on August 12, 2014. Retrieved September 18, 2013.
- ^ a b Lal Shimpi, Anand (December 6, 2012). "iPad 4 (Late 2012) Review: CPU Performance". AnandTech. Archived from the original on May 30, 2013. Retrieved September 17, 2013.
- ^ a b "Inside the Apple iPad 4 – A6X a very new beast!". Chipworks. November 1, 2012. Archived from the original on May 18, 2015. Retrieved September 15, 2013.
- ^ "A few things iOS developers ought to know about the ARM architecture – Wandering Coder". Archived from the original on July 4, 2020. Retrieved July 3, 2020.
- ^ "Apple Introduces iPad mini". Apple. October 23, 2012. Archived from the original on September 12, 2013. Retrieved September 16, 2013.
- ^ Lal Shimpi, Anand; Klug, Brian; Gowri, Vivek (October 16, 2012). "The iPhone 5 Review - Decoding Swift". AnandTech. Archived from the original on December 8, 2012. Retrieved September 17, 2013.
External links
[edit]Apple A6X
View on Grokipediafrom Grokipedia
Overview
Introduction
The Apple A6X is a system-on-a-chip (SoC) designed by Apple Inc. for use in iOS devices, particularly marking a significant upgrade for tablet hardware as the first major iPad-specific processor following the A5X series. It was announced on October 23, 2012, alongside the fourth-generation iPad, positioning the A6X as a pivotal development in Apple's silicon lineup by bridging the capabilities of the phone-focused A6 processor with more powerful tablet requirements.[1] Apple claimed that the A6X delivers up to twice the CPU performance and up to twice the graphics performance compared to the preceding A5X chip, while maintaining the same 10-hour battery life.[1] At its core, the A6X employs a 32-bit ARMv7s architecture featuring Apple's custom Swift CPU cores, configured in a dual-core setup paired with a quad-core GPU to enhance overall processing efficiency for mobile computing tasks.[6]Key Specifications
The Apple A6X is a system on a chip (SoC) featuring the following key technical specifications.| Feature | Specification |
|---|---|
| CPU | Dual-core Swift, based on ARMv7s architecture, clocked at 1.4 GHz.[2][10] |
| GPU | PowerVR SGX554MP4, quad-core configuration.[5] |
| Manufacturing process | 32 nm HKMG (high-k metal gate) by Samsung.[11] |
| Die size | 123 mm².[11][12] |
| Memory support | 1 GB LPDDR2 RAM at 1066 MHz, integrated via package-on-package (PoP) design.[8][13] |
| Other features | Support for integrated LTE modem in compatible devices; video decode engine capable of H.264 up to 1080p.[8][13] |
Design and Architecture
CPU Details
The Apple A6X incorporates a dual-core CPU utilizing Apple's custom Swift microarchitecture, a proprietary design compatible with the ARMv7-A architecture and the ARMv7s instruction set extension. This microarchitecture supports Thumb-2 instructions for code density and NEON SIMD extensions to accelerate multimedia processing tasks such as video decoding and image manipulation. The cores operate at a base clock speed of 1.4 GHz and employ dynamic voltage and frequency scaling (DVFS) to adjust power consumption dynamically based on computational demands, balancing performance and battery life in tablet applications.[2] Each core features a dedicated 32 KB L1 instruction cache and 32 KB L1 data cache for low-latency access to frequently used code and data, paired with a 1 MB shared L2 cache to reduce memory latency across both cores. Compared to the A5X CPU, the A6X delivers up to twice the processing performance while achieving approximately twice the performance at similar power consumption, enabled by the 32 nm manufacturing process and refinements in the Swift design that enhance instructions per cycle through improved branch prediction and pipeline efficiency.[1]GPU and Graphics
The Apple A6X integrates a quad-core Imagination Technologies PowerVR SGX554MP4 graphics processing unit (GPU), an upgrade from the SGX543MP4 in the predecessor A5X, optimized for OpenGL ES 2.0 and subsequent standards to handle complex rendering tasks in mobile applications.[14][2] This GPU operates at a clock speed of 300 MHz, delivering up to 76.8 GFLOPS of processing power, which enables smooth performance at the iPad's 2048×1536 Retina display resolution, including 60 frames per second (fps) in demanding games without frame drops.[14][15] Key to its efficiency is the tile-based deferred rendering (TBDR) architecture, a hallmark of PowerVR designs that minimizes memory bandwidth usage by rendering the scene in small tiles and deferring shading until necessary, thereby reducing power consumption during high-resolution graphics workloads.[16] The SGX554MP4 also employs unified shaders, allowing flexible allocation of processing resources for both vertex and fragment operations, alongside dedicated hardware acceleration for geometry processing to streamline 3D transformations and lighting effects. In video processing, the A6X features a dedicated hardware engine supporting H.264 decode and encode up to 1080p at 30 fps, as well as MPEG-4 playback, with capabilities for dual-stream video handling to enable features like picture-in-picture on compatible displays.[8] Overall, the GPU provides up to twice the graphics throughput of the A5X, making it well-suited for the power and resolution demands of tablet-based Retina displays in gaming and multimedia applications.[14][6]Memory and Integration
The Apple A6X employs 1 GB of LPDDR2-1066 DRAM, configured in two separate 512 MB (4 Gb) modules from Elpida, rather than a stacked package-on-package (PoP) design used in the contemporaneous A6.[17] This arrangement places the memory chips directly on the device's logic board near the SoC, facilitating tight integration through short, high-speed interconnects that help reduce access latency and conserve board space compared to more dispersed layouts.[18] The memory subsystem features a 128-bit interface, doubling the width of the A6's 64-bit controller, paired with Apple's proprietary memory controller to enable efficient data routing across the CPU, GPU, and peripheral I/O components.[18] This custom controller, developed in-house by Apple, optimizes bandwidth allocation and transaction handling for the SoC's demands, achieving a theoretical peak of 17 GB/s—essential for supporting the quad-core GPU's intensive graphics workloads without bottlenecks.[19] Power efficiency in the memory integration is enhanced through support for low-power modes, including self-refresh operations during idle periods, which are coordinated with the SoC's dynamic voltage and frequency scaling (DVFS) framework to dynamically adjust clock speeds and voltages, thereby balancing high-performance bursts with extended battery life.[20] However, the adherence to LPDDR2 standards, without adoption of the faster LPDDR3 introduced in later chips like the A7, inherently caps the maximum bandwidth and efficiency relative to subsequent generations.[21]Development and Manufacturing
Production Process
The Apple A6X system-on-a-chip was fabricated exclusively by Samsung Electronics at its foundries using a 32 nm high-k metal gate (HKMG) process node.[12] This represented Apple's first major deployment of a custom-designed SoC on Samsung's advanced HKMG technology following trials with the related A6 chip, enabling improved power efficiency and performance scaling for mobile applications.[5] The HKMG approach, which incorporates high-dielectric-constant materials and metal gates, allowed for reduced leakage currents and higher transistor speeds compared to prior bulk CMOS processes.[22] Mass production of the A6X commenced in late 2012, aligning with the October launch of the fourth-generation iPad, to support initial demand volumes estimated in the millions of units. Samsung's production ramp benefited from refinements to the 32 nm process, addressing earlier challenges in yield optimization encountered during the A6's initial rollout, through targeted tweaks in lithography and etching stages.[23] The resulting die measures 124 mm² while achieving greater density than the predecessor A5X's 165 mm² die on the coarser 45 nm node, primarily via more efficient block placement and interconnect routing.[12][24] Throughout its lifecycle, the A6X supply chain remained fully dependent on Samsung, with no diversification to alternative foundries like TSMC, which was trialed but not adopted for this chip due to process qualification timelines.[25] This exclusivity highlighted Apple's strategic focus on Samsung's HKMG expertise at the 32 nm scale before shifting toward broader supplier options in subsequent generations. Production of the A6X wound down around 2014, coinciding with the phase-out of the fourth-generation iPad and Apple's migration to the 28 nm A7 and finer nodes beyond.[26]Architectural Basis
The Apple A6X evolved directly from the A5X system on a chip (SoC), maintaining the ARMv7 instruction set architecture as its foundation while introducing Apple's inaugural fully custom CPU cores, dubbed Swift. This shift represented the company's first departure from licensed ARM Cortex designs like the A9 in the A5X, enabling greater optimization for performance and power efficiency tailored to Apple's ecosystem. The custom Swift cores were developed over four years following Apple's 2008 acquisition of P.A. Semi, which provided critical expertise in high-performance, low-power processor design and an architectural license to create proprietary ARM-compatible implementations.[27][28] Drawing heavily from the contemporaneous A6 SoC in the iPhone 5, the A6X applied key lessons in scaling the dual Swift cores to higher clock speeds and integrating a more robust GPU configuration, all while accommodating the larger thermal and power budgets available in tablet form factors. This approach allowed Apple to double CPU and graphics capabilities over the A5X without proportionally increasing die size or power draw, prioritizing balanced efficiency for sustained workloads like video rendering and multitasking. The design retained the 32 nm high-k metal gate (HKMG) process node used in the A6 for cost-effective production scaling.[19][6] Among its innovations, the A6X featured upgraded I/O controllers optimized for the newly introduced Lightning connector, supporting higher data transfer speeds and reversible connectivity while maintaining backward compatibility with legacy accessories. These advancements stemmed from Apple's in-house development of custom peripherals, reducing reliance on third-party IP.[20] The overarching design philosophy of the A6X underscored Apple's commitment to vertical integration, controlling every layer from transistor-level silicon fabrication to application software. This holistic approach facilitated tight optimizations with iOS 6, such as dynamic voltage scaling and workload-specific power gating in the Swift cores, ensuring seamless performance across hardware and software boundaries. Key intellectual property filings in 2012–2013 around the Swift microarchitecture emphasized innovations in manual die layout and branch prediction for power-efficient execution, reflecting Apple's focus on bespoke, high-density designs.[20][27]Performance and Benchmarks
CPU Performance
The Apple A6X processor delivered notable CPU performance for its era, achieving a Geekbench 2 single-core score of approximately 850 and a multi-core score of around 1700 in tests conducted on the iPad (4th generation.[29][30] These results reflected the dual-core Swift architecture's efficiency at 1.4 GHz, enabling smooth execution of scalar tasks without excessive power draw. Compared to the predecessor A5X, the A6X offered up to 1.8 times faster performance in CPU-bound tasks, such as web page rendering and application launches, as verified through cross-generational benchmarks showing a 111% overall uplift in Geekbench scores.[30] This improvement stemmed from architectural optimizations rather than solely clock speed increases, allowing tasks to complete more rapidly and reduce active processing time. In real-world scenarios on iOS 6, the A6X enhanced multitasking by handling multiple background processes with less latency, while Safari's JavaScript execution benefited from a SunSpider benchmark score of 839 ms—over 40% faster than the A5X's approximately 1,500 ms.[31] Efficiency metrics highlighted the A6X's balanced power profile, contributing to 40-50% better battery endurance in mixed workloads compared to the A5X, despite similar 10-hour Wi-Fi usage ratings, as faster task completion minimized idle power consumption.[15] Thermally, the chip sustained its 1.4 GHz clock under sustained loads in the iPad's larger form factor, exhibiting minimal downclocking during prolonged CPU-intensive operations like video encoding.[32] However, its 32-bit ARMv7s architecture limited scalability for memory-intensive applications, foreshadowing the transition to 64-bit designs in subsequent generations that better supported evolving software demands.[6]Graphics Capabilities
The Apple A6X's quad-core PowerVR SGX554MP4 GPU delivers notable rendering performance for its era, achieving scores of approximately 8,600 points in the 3DMark Ice Storm Physics test.[33] These results reflect its capability to handle graphics-intensive tasks efficiently on mobile hardware, outperforming contemporary competitors like the NVIDIA Tegra 4 in similar 3D rendering scenarios.[34] The GPU supports high-resolution Retina display rendering at 2048×1536 resolution and 60 Hz refresh rates, facilitating smooth UI animations and enhanced 3D gaming experiences, such as upgraded performance in titles like Infinity Blade III with stable frame rates at native resolution.[35][31] In multimedia applications, it provides hardware-accelerated decoding and encoding for 1080p H.264 video, enabling seamless playback of high-definition content without significant CPU intervention. Under graphics load, the GPU consumes approximately 2-3 W of power, contributing to the device's overall efficiency and supporting up to 10 hours of continuous 1080p video playback on a full battery charge.[6][1] This power profile balances performance with thermal management in a 32 nm process. Software optimizations in iOS 6 and later leverage the GPU's tile-based deferred rendering (TBDR) architecture for low-overhead rendering, reducing memory bandwidth demands and improving efficiency in OpenGL ES-based applications as precursors to the Metal API.[5][36]Comparisons to Predecessors
The Apple A6X marked a substantial generational leap over its predecessor, the A5X, primarily through architectural enhancements and process improvements that doubled CPU and graphics performance while reducing the overall die size. The A5X utilized dual-core ARM Cortex-A9 processors clocked at 1 GHz and a quad-core PowerVR SGX543MP4 GPU at 250 MHz, fabricated on Samsung's 45 nm process with a die area of approximately 163 mm².[6] In contrast, the A6X introduced Apple's custom dual-core Swift (ARMv7s) processors at 1.4 GHz and a quad-core PowerVR SGX554MP4 GPU at 333 MHz, built on a more efficient 32 nm high-k metal gate process with a 24% smaller die of 123 mm².[12][6] These changes not only boosted computational efficiency but also optimized power delivery for sustained tablet workloads, with the Swift cores providing better instructions per clock than the Cortex-A9 design.[1]| Feature | A5X | A6X |
|---|---|---|
| CPU Cores/Clock | Dual Cortex-A9 @ 1 GHz | Dual Swift @ 1.4 GHz |
| GPU Cores/Clock | Quad SGX543MP4 @ 250 MHz | Quad SGX554MP4 @ 333 MHz |
| Process Node | 45 nm Samsung | 32 nm Samsung HKMG |
| Die Size | 163 mm² | 123 mm² |
| Performance Gain | Baseline | 2× CPU, 2× Graphics |