![]() In the second step, when the multiplexer is done with reading the line number, all of the multiplexers now must go to the line that is corresponding in the cache memory by using the parallel input lines of it.This means that, if the multiplexer needs to read a line number that has a total of L bits, for example, then every multiplexer also should have an equal amount of total number of select lines. In the first step, each of the multiplexers read the specific line number that is generated from the physical address with the help of the select lines in parallel.Implementationĭirect mapping method is used in the direct mapped cache and it follows different steps to implement it. ![]() The rest of the bits of the address are stored as tag values. It also chooses one among all of the available lines once again by using two bits of the address as the index.It chooses a word in the cache line by using two bits of the address as the offset and.The job of the cache controller in a direct mapped cache is very important and it usually plays a dual role such as: ![]() This is mainly because the size of the main memory of the system is much bigger in comparison to the size of the cache. This also means that there will be quite a large number of addresses that will map to that particular location in the cache. This means that in a direct mapped cache, every individual location in the main memory typically maps to one particular location within the cache. The old block, in such situations, is relinquished from the cache.īits are usually taken from the address of the main memory just as it is done while locating a word inside a block in order to describe the particular line where the block is to be stored in the cache. When this line is filled with a memory block, or if it is already filled, it needs a new block to be loaded. In the process of direct cache mapping, each memory block of the main memory of the system is assigned to a specific line in the cache. The line bits are up next in the order of significance and it represents the particular line in the cache where the block is stored.Īnd, finally, all other bits are stored as the tag along with the block which actually finds out the position of the block in the main memory. Out of these, the word bit indicates the particular word in a block memory and is considered to have minimum significance. Understanding Direct Mapped Cacheĭirect mapped cache is the most straightforward way to implement cache.Īctually, in a direct mapped cache, the address is split into three basic parts such as:Īll these particular divisions have specific significance depending on the functions they perform, as mentioned below.
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