PRAM model is relatively older and widely used shared memory computing model for the design and analysis of parallel algorithms and was first developed by Fortune, Wyllie and Goldschlager. A limited numbers of processors share a common global pool of memory. The processors can operate synchronously and allowed to access the memory concurrently and take only one unit of time to be completed. Imposing the restrictions on memory access, the PRAM model has different instances. CRCW PRAM model that permits simultaneous read and write to the same memory cell. CREW PRAM is another model that permits simultaneous read to the same memory cell but permits only one processor to write on a cell at a time. Another model which does not permit the concurrent access of any given memory cell is known as EREW PRAM.
Another model which uses limited communication bandwidth
by calculating maximum memory contention in each phase of
algorithm is known as QSM model. Though the PRAM model
is easy to implement, it suffers from memory and network
contention problem