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Steamroller (microarchitecture)

Microarchitecture by AMD From Wikipedia, the free encyclopedia

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AMD Steamroller Family 15h is a microarchitecture developed by AMD for AMD APUs, which succeeded Piledriver in the beginning of 2014 as the third-generation Bulldozer-based microarchitecture.[2] Steamroller APUs continue to use two-core modules as their predecessors, while aiming at achieving greater levels of parallelism.

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Microarchitecture

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Steamroller still features two-core modules found in Bulldozer and Piledriver designs called clustered multi-thread (CMT), meaning that one module is marketed as a dual-core processor.[3] The focus of Steamroller is for greater parallelism.[4] Improvements center on independent instruction decoders for each core within a module, 25% more of the maximum width dispatches per thread, better instruction schedulers, improved perceptron branch predictor, larger and smarter caches, up to 30% fewer instruction cache misses, branch misprediction rate reduced by 20%, dynamically resizable L2 cache, micro-operations queue,[5] more internal register resources and improved memory controller.

AMD estimated that these improvements will increase instructions per cycle (IPC) up to 30% compared to the first-generation Bulldozer core while maintaining Piledriver's high clock rates with decreased power consumption.[3] The final result was a 9% single-threaded IPC improvement, and 18% multi-threaded IPC improvement over Piledriver.[6]

Steamroller, the microarchitecture for CPUs, as well as Graphics Core Next, the microarchitecture for GPUs, are paired together in the APU lines to support features specified in Heterogeneous System Architecture.

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History

In 2011, AMD announced a third-generation Bulldozer-based line of processors for 2013,[7] with Next Generation Bulldozer as the working title, using the 28 nm manufacturing process.[8]

On 21 September 2011, leaked AMD slides indicated that this third generation of Bulldozer core was codenamed Steamroller.[9][10]

In January 2014, the first Kaveri APUs became available.[11]

Starting from May 2015 till March 2016 new APUs were launched as Kaveri-refresh (codenamed Godavari).[12]

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Features

The following table shows features of AMD's processors with 3D graphics, including APUs (see also: List of AMD processors with 3D graphics).

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  1. For FM2+ Excavator models: A8-7680, A6-7480 & Athlon X4 845.
  2. A PC would be one node.
  3. An APU combines a CPU and a GPU. Both have cores.
  4. Requires firmware support.
  5. Requires firmware support.
  6. No SSE4. No SSSE3.
  7. Single-precision performance is calculated from the base (or boost) core clock speed based on a FMA operation.
  8. To play protected video content, it also requires card, operating system, driver, and application support. A compatible HDCP display is also needed for this. HDCP is mandatory for the output of certain audio formats, placing additional constraints on the multimedia setup.
  9. To feed more than two displays, the additional panels must have native DisplayPort support.[22] Alternatively active DisplayPort-to-DVI/HDMI/VGA adapters can be employed.
  10. DRM (Direct Rendering Manager) is a component of the Linux kernel. Support in this table refers to the most current version.
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Processors

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APU lines

  1. Kaveri A-series APU
  2. Berlin APU - canceled
    • Announced in 2013 by AMD[36] the Berlin APU were targeted at the enterprise and server markets featuring four Steamroller cores, up to 512 stream processors and support for ECC memory.

FX lines (discontinued)

In November 2013 AMD confirmed it would not update the FX series in 2014, neither its Socket AM3+ version, nor will it receive a Steamroller version with a new socket.[37][38]

AMD however, released a Kaveri based FX-770K for desktop and FX-7600P for mobile which are basically APUs with their integrated graphics disabled similar to the Athlon X4 FM2+ line. Those APUs were released for OEMs only.

Server lines (canceled)

AMD's server roadmaps for 2014 showed:[39][40]

  • Berlin APU - quad-core x86 Steamroller architecture (as described above) for 1 Processor (1P) compute and media clusters
  • Berlin CPU - quad-core x86 Steamroller architecture for 1P web and enterprise services clusters
  • Seattle CPU - 4/8 core AArch64 Cortex-A57 architecture (Opteron A1100) for 1P web and enterprise services clusters [41]
  • Warsaw CPU - up to 16 core x86 Piledriver (2nd gen Bulldozer) architecture (Opteron 6338P and 6370P) for 2P/4P servers [42]

However, plans for Steamroller Opteron products were cancelled, likely due to the poor energy efficiency achieved in this generation of the Bulldozer architecture. Energy efficiency was greatly increased in the following generation, Excavator, which exceeded Jaguar in performance per watt, and approximately doubled performance/watt over Steamroller (for example 20.74 pt/W vs 10.85 pt/W when comparing similar mobile APUs using rough arbitrary metrics).[43][44]

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References

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