UMA vs. NUMA Computers



  UMA vs. NUMA Computers.ppt (Size: 232 KB / Downloads: 0)

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