Relaxed Consistency Models Rules. X-Y: Operation X must complete before operation y is done Sequential consistency requires(sC): R→W,R→R.W→R.W→W IBM-370 Relax w→R(TSO) TSO Total store ordering"(X86) PS Relax W→W(Pso) 1---------- “ Partia| store order (V RMO PowerPC RCI Re|axR→ Wandr→R Figure 2.24: Relationship among models according to the "stricter"relation Weak ordering" and"release consistency Relax→R,R→W,W-R,W→W(RMO) Release Memory Ordering Maintains the program order to access the same location W→R.W→W 2021/2/11 计算机体系结构Relaxed Consistency Models • Rules: – X → Y :Operation X must complete before operation Y is done 2021/2/11 计算机体系结构 9 Relax R → W and R → R “Weak ordering” and “release consistency” Relax R → R , R → W , W-R, W → W (RMO) “Release Memory Ordering” Maintains the program order to access the same location: W →R, W → W Relax W → R (TSO) “Total store ordering” (X86) Relax W → W (PSO) “Partial store order” Sequential consistency requires (SC) : R → W, R → R, W → R, W → W