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UMA vs. NUMA Computers - baluz - 10-06-2017 UMA vs. NUMA Computers [attachment=292] Distributed Memory Computers Distributed memory computers use: Message Passing Model Explicit message send and receive instructions have to be written by the programmer. Send: specifies local buffer + receiving process (id) on remote computer (address). Receive: specifies sending process on remote computer + local buffer to place data. Advantages of Message-Passing Communication Hardware for communication and synchronization are much simpler: Compared to communication in a shared memory model. Explicit communication: Programs simpler to understand, helps to reduce maintenance and development costs. Synchronization is implicit: Naturally associated with sending/receiving messages. Easier to debug. Disadvantages of Message-Passing Communication Programmer has to write explicit message passing constructs. Also, precisely identify the processes (or threads) with which communication is to occur. Explicit calls to operating system: Higher overhead. DSM Physically separate memories are accessed as one logical address space. Processors running on a multi-computer system share their memory. Implemented by operating system. DSM multiprocessors are NUMA: Access time depends on the exact location of the data. Different SMP Organizations Processor and cache on separate extension boards (1980s): Plugged on to the backplane. Integrated on the main board (1990s): 4 or 6 processors placed per board. Integrated on the same chip (multi-core) (2000s): Dual core (IBM, Intel, AMD) Quad core |