Embedded Systems Design - August 2008 - (Page 30) 0808esd.p30to33 7/17/08 11:54 AM Page 30 feature Here’s an example of how the Open Core Protocol was used to reconfigure the basic MIPS32 architecture to support cache-coherent traffic within an embedded multicore cluster. Achieving BY MATTHIAS KNOTH cache coherence in a MIPS32 H 30 istorically, memory coherence in multiprocessor systems was often achieved through bus “snooping,” where each core was connected to a common multitier bus and was able to snoop on memory-access traffic of processor peers to regulate the coherence status of individual cache lines. For that, each core maintained the coherence status of L1 cache lines locally and posted status changes to peers via the common bus. The increasing size and complexity of the system-on-a-chip (SoC) led to restructuring of the multitier-bus philosophy in favor of localized point-to-point connections with centralized traffic routing. This configuration enabled speed and power improvements on now localized bus segments due to reduced load and segment length. Also, buscontention problems eased, and throughput increased for the localized data exchange. In response to this trend in system architecture, the Open Core Protocol (OCP) standard emerged to consolidate this design philosophy. Further, emergence of IP-provider business models catalyzed the standardization of IP interconnect and design methods to facilitate design reuse centered on an open standard. However, localized bus transactions, as conducted through OCP interconnect segments, decouple processors throughout a multicore cluster. Coherence schemes cannot be directly based on bus snooping and reliance on bus arbitration to ensure access ordering. Different methods of communication are needed to ensure data is accessed consistently. Additional challenges arise in the ordering of competing L1-line data requests. One way to address these challenges is to add AUGUST 2008 | embedded systems design | www.embedded.com http://www.embedded.com
Table of Contents Feed for the Digital Edition of Embedded Systems Design - August 2008 Embedded Systems Design - August 2008 Contents Number Include Parity Bit Programmer's Toolbox Cover Feature: Virtualization for Embedded X86 Multiprocessor Applications Wanted: Industry Standards for Benchmarking Embedded VMM Hypervisors Achieving Cache Coherence in a MIPS32 Multicore Design Memory Allocation in C Advertising Index Break Points Marketplace Embedded Systems Design - August 2008 Embedded Systems Design - August 2008 - Embedded Systems Design - August 2008 (Page Cover1) Embedded Systems Design - August 2008 - Embedded Systems Design - August 2008 (Page Cover2) Embedded Systems Design - August 2008 - Embedded Systems Design - August 2008 (Page 1) Embedded Systems Design - August 2008 - Embedded Systems Design - August 2008 (Page 2) Embedded Systems Design - August 2008 - Contents (Page 3) Embedded Systems Design - August 2008 - Contents (Page 4) Embedded Systems Design - August 2008 - Number Include (Page 5) Embedded Systems Design - August 2008 - Number Include (Page 6) Embedded Systems Design - August 2008 - Number Include (Page 7) Embedded Systems Design - August 2008 - Number Include (Page 8) Embedded Systems Design - August 2008 - Parity Bit (Page 9) Embedded Systems Design - August 2008 - Parity Bit (Page 10) Embedded Systems Design - August 2008 - Programmer's Toolbox (Page 11) Embedded Systems Design - August 2008 - Programmer's Toolbox (Page 12) Embedded Systems Design - August 2008 - Programmer's Toolbox (Page 13) Embedded Systems Design - August 2008 - Programmer's Toolbox (Page 14) Embedded Systems Design - August 2008 - Programmer's Toolbox (Page 15) Embedded Systems Design - August 2008 - Cover Feature: Virtualization for Embedded X86 Multiprocessor Applications (Page 16) Embedded Systems Design - August 2008 - Cover Feature: Virtualization for Embedded X86 Multiprocessor Applications (Page 17) Embedded Systems Design - August 2008 - Cover Feature: Virtualization for Embedded X86 Multiprocessor Applications (Page 18) Embedded Systems Design - August 2008 - Cover Feature: Virtualization for Embedded X86 Multiprocessor Applications (Page 19) Embedded Systems Design - August 2008 - Cover Feature: Virtualization for Embedded X86 Multiprocessor Applications (Page 20) Embedded Systems Design - August 2008 - Cover Feature: Virtualization for Embedded X86 Multiprocessor Applications (Page 21) Embedded Systems Design - August 2008 - Cover Feature: Virtualization for Embedded X86 Multiprocessor Applications (Page 22) Embedded Systems Design - August 2008 - Cover Feature: Virtualization for Embedded X86 Multiprocessor Applications (Page 23) Embedded Systems Design - August 2008 - Cover Feature: Virtualization for Embedded X86 Multiprocessor Applications (Page 24) Embedded Systems Design - August 2008 - Cover Feature: Virtualization for Embedded X86 Multiprocessor Applications (Page 25) Embedded Systems Design - August 2008 - Cover Feature: Virtualization for Embedded X86 Multiprocessor Applications (Page 26) Embedded Systems Design - August 2008 - Wanted: Industry Standards for Benchmarking Embedded VMM Hypervisors (Page 27) Embedded Systems Design - August 2008 - Wanted: Industry Standards for Benchmarking Embedded VMM Hypervisors (Page 28) Embedded Systems Design - August 2008 - Wanted: Industry Standards for Benchmarking Embedded VMM Hypervisors (Page 29) Embedded Systems Design - August 2008 - Achieving Cache Coherence in a MIPS32 Multicore Design (Page 30) Embedded Systems Design - August 2008 - Achieving Cache Coherence in a MIPS32 Multicore Design (Page 31) Embedded Systems Design - August 2008 - Achieving Cache Coherence in a MIPS32 Multicore Design (Page 32) Embedded Systems Design - August 2008 - Achieving Cache Coherence in a MIPS32 Multicore Design (Page 33) Embedded Systems Design - August 2008 - Achieving Cache Coherence in a MIPS32 Multicore Design (Page 34) Embedded Systems Design - August 2008 - Memory Allocation in C (Page 35) Embedded Systems Design - August 2008 - Memory Allocation in C (Page 36) Embedded Systems Design - August 2008 - Memory Allocation in C (Page 37) Embedded Systems Design - August 2008 - Memory Allocation in C (Page 38) Embedded Systems Design - August 2008 - Memory Allocation in C (Page 39) Embedded Systems Design - August 2008 - Memory Allocation in C (Page 40) Embedded Systems Design - August 2008 - Memory Allocation in C (Page 41) Embedded Systems Design - August 2008 - Memory Allocation in C (Page 42) Embedded Systems Design - August 2008 - Advertising Index (Page 43) Embedded Systems Design - August 2008 - Advertising Index (Page 44) Embedded Systems Design - August 2008 - Break Points (Page 45) Embedded Systems Design - August 2008 - Break Points (Page 46) Embedded Systems Design - August 2008 - Marketplace (Page 47) Embedded Systems Design - August 2008 - Marketplace (Page 48) Embedded Systems Design - August 2008 - Marketplace (Page Cover3) Embedded Systems Design - August 2008 - Marketplace (Page Cover4)
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