A Closer Look (Read) I
•Postulate
1 processor per node, 1 level cache, local MSI protocol [from last week]
•On a
read access fault at Px, the local directory controller determines
if block is locally/remotely allocated
•If
local, it delivers data
•If
remote it finds the home … by high order bits probably
•Controller
sends request to home node for blk
•Home
controller looks up directory entry for blk
•Dirty
bit OFF, controller finds blk in memory, sends reply, sets xth presence bit ON