Shared memory multiprocessor: In this type of multiprocessor architecture, memory is shared between all the computers. RAM is common for all the CPUs which are connected in this system. Computers can read and write to the common memory locations. The process of read and write is controlled by using different algorithms. A computer can read from and write to in the memory by using LOAD and STORE instructions. This type of architecture is a bit difficult to create and thus are expensive.
Message passing multicomputer: In this type of multicomputer architecture, every CPU is connected with a memory and which are then connected by using a high speed interconnect. This interconnect is used for sending and receiving messages between the CPUs. The memory of a CPU is local for that particular CPU and can’t be accessed by another CPU. This type of architecture is easier to create and thus are comparatively cheaper. Since they use cluster of computers they are also known as COWS (Clusters of Workstations).