2/16/2016 Chapter Four Array Computers

Index Objective understand the meaning and structure of array computer realize the associated instruction sets, interprocessor communication etc. manifest the direction of array computers

Index Historic background SOLOMON and ILLIAC Burroughs Scientific Processor - capable of performing 50 MFLOP STARAN resides in 32 array modules each of which contains 256 PEs. ICL DAP is an SIMD having a total of 4096 processors in a 64 x 64 matrix.

Index Terminology AE –Arithmetic elements AP –Arithmetic processors AM –Array memory CP Control processor. The control unit

Index Characteristics of a processor array A regular lattice of processors in one or more dimensions Most of the processors in SIMD computer are simple in its structure Each processor has access to a block of a local memory Each processor has data connections to its nearest neighbours. At a given moment all processors execute the same instruction

Index Organization of an array computer ILLIAVC is the machine that utilizes the approach of array processor. The arithmetic processors execute the instructions making use of their local memories. Control unit.

Index Control Unit & AP

Index Communications amongst processor arrays Complete connection network Cyclically connected

Index Complete connection

Index Cyclic Connection

Index Memory access mechanism deals with problems of accessing the shared memory by the arithmetic processors. If the memory is blocked because it is used by other arithmetic processor. The processor has to wait until it is released.

Index Straight Storage Place the memory cell as it is.

Index Skewed storage Skewed storage means the shift of storage cell.

Index Array computers in perspective The computation must be describable by vector instructions High-speed data routing between processors must be possible Operands to be manipulated simultaneously must be capable of being fetched simultaneously The future approach for array processors is to increase their flexibility while retaining their efficiency for vector computations.

Index Summary array computer is formed by a single control unit and a number of arithmetic processors. Array computer is an example of SIMD model The arithmetic processors are linked up through a communication network. Each processor can access the memory storage locally or through the network.