Le to have an even greater cache hierarchy than two levels. given the processor above with a second level, direct-mapped cache, a designer wants to add a third level cache that takes 50 cycles to access and will reduce the global miss rate to 1.3%. would this provide better performance? in general, what are the advantages and disadvantages of adding a third level cache?

It definitely provide a better performance due to be a specialized memory.

Explanation:

It's memory specialized that helps improve the performance of Cache Levels L1 and L2 when an instruction is searched for in L3 it is eventually elevated to a cache level of a higher level.

Advantages:

Faster than main memory (RAM)

Helps the system store a large amount of information.

Streamlines processor tasks

Speeds up access to data and instructions that were not located on L1 or L2.

It's a more specialized.

Disadvantage :

It's slower and bigger than L2

It has no significant disadvantages

It's not expensive.  

It's a volatile memory .