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Single-Chip Multi-Processors (CMP). Bharath Ambale Venkatesh 10/24/2007. Trends. Increasing processor size/speed leads to increase in power required Increasing heat generated leads to need of cooling components Increase in network speeds is much slower than increase in processor speeds
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Single-Chip Multi-Processors(CMP) Bharath Ambale Venkatesh 10/24/2007 Ambale: CMP
Trends • Increasing processor size/speed leads to increase in power required • Increasing heat generated leads to need of cooling components • Increase in network speeds is much slower than increase in processor speeds • Future applications are becoming more and more parallel – multimedia, face recognition, voice recognition, etc… • Future applications also becoming data intensive Ambale: CMP
Instruction-level parallelism (ILP) • Re-ordering of instructions so that they can be executed in parallel • Pipelining • Superscalars • Maximum of 6-10 instructions per cycle for real applications • Bottlenecks: Branch prediction Ambale: CMP
Thread-level parallelism (TLP) • Multiple threads spawned from same process (SMT) • Loop-level parallelism • Threads interact with each other • Pentium 4 uses hyper-threading • Bottleneck: Memory cache Ambale: CMP
Process-level Parallelism (PLP) • Run multiple independent processes controlled by the OS • Symmetric Multiprocessors (SMP) : multiple independent processors connected by a network (cluster) • Bottleneck: network Ambale: CMP
Memory Access • Cache miss: when data has to fetched from main memory • Cache miss in superscalars leads to significant delay • SMT leads to multiple processes accessing a shared cache – a cache is pushed to have more ports • Memory bandwidth is a problem Ambale: CMP
CMP • Introduce multiple supersacalar processors each capable of running multiple threads • Each processor has individual cache and also has a shared cache • Processors need not be homogenous Ambale: CMP
CMP • Advantages • Multi-tasking • Shorter signal path • Less-power consumed • Memory bandwidth is not the limiting problem • Disadvantages • Specialized software to utilize multithreading • Thermal management is more difficult • Commercial CMP’s • Intel and AMD’s dual-core, quad-core,.. Ambale: CMP
Cell Processor Ambale: CMP
References • "A D&T Roundtable: Are Single-Chip Multiprocessors in Reach?," IEEE Design and Test of Computers ,vol. 18, no. 1, pp. 82-89, January/February, 2001. • Wenbin Yao, Dongsheng Wang, Weimin Zheng, Songliu Guo. “Current Trends in High Performance Computing and Its Applications.” Architecture Design of a Single-chip Multiprocessor , pp. 165-174, 2005. • L. Hammond, B. Nayfeh, and K. Olukotun. "A single-chip multiprocessor." IEEE Computer, vol. 30, no. 9, pp. 79--85, September 1997. Ambale: CMP