PPC b4 (BasicFour) "Simple sync test, light barrier and isync" {0:r6=1; 0:r4=x; 0:r5=y; 1:r4=x; 1:r5=y; x=0; y=0;} P0 | P1 ; stw r6,0,r4 | lwz r1,0,r5 ; lwsync | isync ; stw r6,0,r5 | lwz r2,0,r4 ; Observed 1:r1=1; 1:r2=0;