Editing Distributed shared memory (section)

===Comparison with message passing ===
{| class="wikitable"
|-
! Message passing
! Distributed shared memory
|-
| Variables have to be marshalled
| Variables are shared directly
|-
| Cost of communication is obvious
| Cost of communication is invisible
|-
| Processes are protected by having private address space
| Processes could cause error by altering data
|-
| Processes should execute at the same time
| Executing the processes may happen with non-overlapping lifetimes
|}

Software DSM systems also have the flexibility to organize the shared memory region in different ways. The page based approach organizes shared memory into pages of fixed size. In contrast, the object based approach organizes the shared memory region as an abstract space for storing shareable objects of variable sizes. Another commonly seen implementation uses a [[tuple space]], in which the unit of sharing is a [[tuple]].

[[Shared memory architecture]] may involve separating memory into shared parts distributed amongst nodes and main memory; or distributing all memory between nodes. A [[coherence protocol]], chosen in accordance with a [[consistency model]], maintains [[memory coherence]].