P = 64 -> 64 bits per cache line to keep track of which node has the line in cache. 64 bits = 8 bytes overhead in addition to the 64 original bytes in memory is a 8/64 = 12.5% overhead.
Similarly:
P = 256 -> (256/8)/64 = 50% overhead
P = 1024 -> (1024/8)/64 = 200% overhead
pk267
How were we getting 30 bits for storing the directory here (it was discussed in class)?
How is overhead computed here?
I think it's computed like this:
P = 64 -> 64 bits per cache line to keep track of which node has the line in cache. 64 bits = 8 bytes overhead in addition to the 64 original bytes in memory is a 8/64 = 12.5% overhead.
Similarly:
P = 256 -> (256/8)/64 = 50% overhead
P = 1024 -> (1024/8)/64 = 200% overhead
How were we getting 30 bits for storing the directory here (it was discussed in class)?