Full Map Directory Scheme
Each directory entry contains as many pointers as there are other caches (processors) in the system
- If there are 32 processors in the system, then each pointer could be represented by one bit. Bit 0 would be for processor 0, bit 1 for processor 1, etc. These bits are the ‘present’ bits. Other status bits are kept as well (write-permission).
Problem: wasted space in directory if actual number of processors in the system is less than the possible maximum number of processors
- Experience shows that at any given time, a particular data block is held by only a few processors.