Steamroller (microarchitecture)

Steamroller is a microarchitecture under development by AMD, intended to succeed Piledriver in the second half of 2013.^[2] Steamroller APUs will continue to use two-core modules as their predecessors, while aiming at achieving greater levels of parallelism.

Overview

Steamroller will still feature two-core modules found in Bulldozer and Piledriver designs.^[2] The focus of Steamroller is for greater parallelism.^[3] Improvements will 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% less instruction cache misses, branch misprediction rate reduced by 20%, dynamically resizable L2 cache, micro-operations queue,^[4] more internal register resources and improved memory controller.

AMD estimates that these improvements will increase instructions per cycle (IPC) up to 30% while maintaining Piledriver high clock rates with decreased power consumption.^[2]

History

In 2011, AMD announced a third-generation Bulldozer-based line of processors for 2013,^[5] with Next Generation Bulldozer as the working title, using the 28 nm manufacturing process.^[6]

On 21 September 2011, leaked AMD slides indicated that this third generation of Bulldozer core was codenamed Steamroller.^[7][8]

In January 2014, Kaveri APUs became available.^[9]

Processors

APU lines

There are two main APU lines announced:

1. Kaveri A-series APU
   • Desktop budget and mainstream markets (FM2+): The Trinity / Richland APU line is scheduled to be replaced on 14 January 2014 by the Kaveri APU line, as the third generation of A10, A8, A6 and A4 series for the desktop market. Currently known new model is a quad-core A10-7850K APU, with a 3.7 GHz core frequency and 4 MB L2 cache, incorporating a 720 MHz GPU with 512 stream processors and 856 GFLOPS of total processing power.^[10]
     These APUs have two to four enhanced Steamroller B cores, a GCN 1.1 Volcanic Islands integrated GPU,^[11][12] and two integrated DDR3 memory controllers. Kaveri APUs utilize the new FM2+ socket, thus they are not backwards compatible with the previous generation of FM2 motherboards.^[13]
   • Notebook mainstream and performance markets: The same features as described in the desktop budget and mainstream markets. The platform will be codenamed Indus, while the fusion controller hub (FCH) will be codenamed Bolton.
2. Berlin APU
   • Enterprise and server markets: The Berlin APU will be similar to Kaveri, featuring four Steamroller cores, up to 512 stream processors, and support for ECC memory.^[14]

FX lines

In November 2013, AMD confirmed it will not update the FX series in 2014, neither its current Socket AM3+ version, nor will it receive a Steamroller version with a new socket.^[15][16] An unconfirmed article citing anonymous sources with knowledge of AMD's internal roadmap extending into 2015, also did not mention plans for a new FX processor.^[17]

Server lines

AMD's server roadmaps for 2014 are showing only the above described quad-core Steamroller Berlin APU, and a Piledriver-based Warsaw CPU having up to 16 cores.^[18]

References