Branch Micro-Architecture of an Embedded Processor with Split Branch Architecture for Digital Consumer Products

Naohiko IRIE  Fumio ARAKAWA  Kunio UCHIYAMA  Shinichi YOSHIOKA  Atsushi HASEGAWA  Kevin IADONATE  Mark DEBBAGE  David SHEPHERD  Margaret GEARTY  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E85-C    No.2    pp.315-322
Publication Date: 2002/02/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on High-Performance and Low-Power Microprocessors)
Category: High-Performance Technologies
Keyword: 
embedded processor,  SIMD,  preload,  branch prediction,  

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Summary: 
An embedded processor core using split branch architecture has been developed. This processor core targets 400 MHz using 0.18 µm technology, and its higher frequency needs deeper pipeline than the conventional processor. To solve the increasing branch penalty problem caused by a deeper pipeline, this processor takes an active preload mechanism to preload the target instructions to internal buffers in order to hide the instruction cache latency. The processor also uses multiple instruction buffers to reduce branch penalty cycles of branch misprediction. The performance estimation result shows that about 70% of branch overhead cycles can be reduced from the conventional implementation. The area for this branch mechanism consumes only 1% of the total core, which is smaller than the conventional branch target buffer (BTB) scheme, and helps to achieve low power and low cost.