Bobcat (microarchitecture)

Lore & Background

The Bobcat microarchitecture was developed by AMD for its accelerated processing units (APUs) under the 'Fusion' brand. It was revealed during a speech from AMD executive vice-president Henri Richard at Computex 2007 and entered production in Q1 2011. Executive vice-president Mario A. Rivas was a major supporter, believing it was difficult to compete in the x86 market with a single core optimized for the 10–100 W range, and actively promoted the development of the simpler core with a target range of 1–10 W. It was believed that the core could migrate into the hand-held space if power consumption could be reduced to less than 1 W.

A simplified architecture diagram was released at AMD's Analyst Day in November 2009. The design is similar in concept to earlier AMD research in 2003, detailing the specifications and advantages of extending x86 'everywhere'. The Bobcat x86 CPU core design has since been completed and implemented in AMD APU processor products with a TDP of 18 W or less. Since its launch, Bobcat-based CPUs have also been used by OEMs on larger laptops.

Architecture specifics include a 64-bit core with out-of-order execution, an advanced branch predictor, a dual x86 instruction decoder, a 64-bit integer unit with two ALUs, a floating-point unit with two 64-bit pipes, a single channel 64-bit memory controller, 32 KiB instruction plus 32 KiB data L1 cache, and 512 KiB to 1 MiB L2 cache. It supports MMX, SSE, SSE2, SSE3, SSSE3, SSE4A, and ABM. In February 2013, AMD detailed plans for a successor codenamed Jaguar.

Reader's Guide

Bobcat represents AMD's strategic entry into the low-power x86 market, directly addressing the need for energy-efficient cores in netbooks, ultra-portable laptops, consumer electronics, and embedded systems. Its development was driven by the recognition that competing in the x86 market with a single core optimized for 10–100 W was difficult, leading to the creation of a simpler core targeting 1–10 W. The microarchitecture enabled AMD to produce APUs with a TDP of 18 W or less, combining CPU and GPU cores under the Fusion brand.

The core's design, with out-of-order execution and a dual decoder, aimed to deliver adequate performance while minimizing power consumption. The potential for migration into the hand-held space, if power could be reduced below 1 W, highlighted its long-term ambition. Bobcat's implementation in E-Series, C-Series, and G-Series processors allowed OEMs to use it in a range of devices, including larger laptops. Its successor, Jaguar, was announced in February 2013, indicating AMD's continued investment in this low-power architecture. Bobcat's legacy lies in proving that x86 could scale down to very low power envelopes, opening new markets for the architecture.