I understand strict and sequential consistency independently fairly well.
Strict C basically enforces the actual order in which the instructions ran on the global clock.
Sequential Consistency basically enforces the order only on one processor.
I'm having trouble putting together some literature though. http://www.cs.nmsu.edu/~pfeiffer/classes/573/notes/consistency.html describes sequential consistency as allowing for memory 'lag'. It may take time for a write to propagate across all processors. But when it does, it reaches all of them at once which is fine. Thus, the following is valid under Sequential Consistency
P1: W(x)1 ----------------------- P2: R(x)0 R(x)1
What concerns me now is the following processes, which is something like Dekker's algorithm.
P1: W(x)1 R(y)0 ----------------- P2: W(y)1 R(x)0
This should surely NOT be possible under Sequential consistency ( http://portal.acm.org/citation.cfm?id=1787234.1787255 pg 2). There is no total order that can give this result.
But it makes sense from the idea that sequential consistency allows writes to propagate slowly and one thread may not have any idea as to what other processors are up to.
What am I missing here?