Memory Consistency
•What should it mean for processors to
see a consistent
view of memory?
•Coherency is too weak because it only requires
ordering with respect to individual locations, but there are other ways of
binding values together
P0 : [a, flag initially 0]
a := 1;
flag := 1;
P1 :
while(flag != 1)do; -- spin
print (a);
Coherency requires only that the 0 --> 1
transition
of a be seen eventually by P1