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Cache placement policies
Cache placement policies are policies that determine where a particular memory block can be placed when it goes into a CPU cache. A block of memory cannot necessarily be placed at an arbitrary location in the cache; it may be restricted to a particular cache line or a set of cache lines by the cache's placement policy.
There are three different policies available for placement of a memory block in the cache: direct-mapped, fully associative, and set-associative. Originally this space of cache organizations was described using the term "congruence mapping".
In a direct-mapped cache structure, the cache is organized into multiple sets with a single cache line per set. Based on the address of the memory block, it can only occupy a single cache line. The cache can be framed as a n × 1 column matrix.
Consider a main memory of 16 kilobytes, which is organized as 4-byte blocks, and a direct-mapped cache of 256 bytes with a block size of 4 bytes. Because the main memory is 16kB, we need a minimum of 14 bits to uniquely represent a memory address.
Since each cache block is of size 4 bytes, the total number of sets in the cache is 256/4, which equals 64 sets.
The incoming address to the cache is divided into bits for Offset, Index and Tag.
Below are memory addresses and an explanation of which cache line they map to:
In a fully associative cache, the cache is organized into a single cache set with multiple cache lines. A memory block can occupy any of the cache lines. The cache organization can be framed as 1 × m row matrix.
Hub AI
Cache placement policies AI simulator
(@Cache placement policies_simulator)
Cache placement policies
Cache placement policies are policies that determine where a particular memory block can be placed when it goes into a CPU cache. A block of memory cannot necessarily be placed at an arbitrary location in the cache; it may be restricted to a particular cache line or a set of cache lines by the cache's placement policy.
There are three different policies available for placement of a memory block in the cache: direct-mapped, fully associative, and set-associative. Originally this space of cache organizations was described using the term "congruence mapping".
In a direct-mapped cache structure, the cache is organized into multiple sets with a single cache line per set. Based on the address of the memory block, it can only occupy a single cache line. The cache can be framed as a n × 1 column matrix.
Consider a main memory of 16 kilobytes, which is organized as 4-byte blocks, and a direct-mapped cache of 256 bytes with a block size of 4 bytes. Because the main memory is 16kB, we need a minimum of 14 bits to uniquely represent a memory address.
Since each cache block is of size 4 bytes, the total number of sets in the cache is 256/4, which equals 64 sets.
The incoming address to the cache is divided into bits for Offset, Index and Tag.
Below are memory addresses and an explanation of which cache line they map to:
In a fully associative cache, the cache is organized into a single cache set with multiple cache lines. A memory block can occupy any of the cache lines. The cache organization can be framed as 1 × m row matrix.