L-3.8: Fully Associative Mapping with examples in Hindi | Cache Mapping | Computer Organisation

In fully associative mapping,
A block of main memory can be mapped to any freely available cache line.
This makes fully associative mapping more flexible than direct mapping.
A replacement algorithm is needed to replace a block if the cache is full.

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[arijitbarua]

I went through your entire playlist..u are just doing an incredible job..u r GOD for all engineering students as well as BCA students

[yamisharma]

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[tanishqvyas]

Aap jaise content creators hai jo hum logo ko humare college se jyada accha padha rhe hain. Please keep up the good work. Aapka padhaya hua bahut acche se samajh aata hai. Thank You : )

[animationcrust]

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[vaibhavmalpani]

Thank God ... I found this video on time ... Aap bhagvaan ho sir ... Thank you so much ... Aapne COA ka dar nikal diya pura ... Love from Mumbai💗

[abhishekabhishekgond]

Thank you sir, it was really good understanding video..

[hamid_ra.za]

What is Fully Associative Mapping?
“Every memory block can be mapped to any cache line.”

The fully associative mapping helps us resolve the issue related to conflict misses. It means that any block of the main memory can easily come in a line of cache memory. Here, for instance, B0 can easily come in L1, L2, L3, and L4. Also, the case would be similar for all the other blocks. This way, the chances of a cache hit increase a lot.

Now, let us assume that there is a RAM (Main Memory) size of 128 Words along with a Cache size of 16 Words. Here, the Cache and the Main Memory are divided into Lines and blocks, respectively. Every block Line is of the size 4- words. It is shown in the vdo given as follows:
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Physical Address
Since the main memory has a size of 128 words, a total of 7 bits would be used for representing the main memory. Thus, the Physical address would be 7 bits in size. Given below is an example of the fully associative mapping of W24 of the B6:
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Since the Block offset represents the Block size, 4 words of Block could be represented through two bits.
Since the Block Number represents the Block in the main memory, there are a total of 32 blocks in the main memory. Thus, 5 bits would be required here to represent 32 blocks. We do not need to divide the Block Number into Line Numbers and tags. It is because, in any cache Line, any main memory block can come.
Thus, Block Number is our Tag. A tag represents the Block Number as the 32 blocks’ main memory. Also, any block can come in a cache line. This way, any block can come from 32 memory blocks in any cache line. Thus, 5 bits would be required whenever we want to represent a block in a cache line.
Note: In case there are a total of 128 blocks, and the size of every block is 8 words, then,

Tag= 7 bits

Block number = 7 bits

Block offset = 3 bits
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Searching for a Block through Tags (Cache Hit or Cache Miss)
Suppose that a CPU generates an address for a main memory of 128-word. The first two bits (00) here would represent the Block offset, and the last five bits here would represent the Tag in Cache memory.

Since the required word of the memory block can be present in a line of cache, the number of the comparator is increased. Here, we match the tag of the given address with the tags of all the cache lines. In case it matches, then it’s a case of a cache hit, or else, it is a case of a cache miss.

Here is the Cache Hit for the address
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Shortcut Formulas

Comparator = Total number of lines
Physical Address (PA) = Block Offset + Tag
The value of the comparator in a fully associative mapping is equal to the total number of lines. It is because any main memory block can come in any line. This way, we can compare the tag of the given address with the tag of each and every line in the cache.

[nirdhast]

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[Im_Urs-qslr]

What an explanation sir. Simply superb.

[ayushisrivastava]

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[akansharajput_]

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[arno]

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YOU SAVED MY LIFE (T~T)

[nilotpaldas]

The same topic in my college was made to look like rocket science

[erpoonamsatani]

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[nasrinaktar]

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[aayushisinghal]

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[waron]

Before this video please see video 3.9 for better understanding😊.

[Bhubaneswar_Sandha]

sir, aap ko zindegi me ek baar jaroor milenge aur aapke charan chunke aasirbad jarur lenge .. agar sach me 1 saal pehle pata hota ki itni achi explanatory video youtube par he then believe me baht gain hota...

[nothing-cers]

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Mny yahi seekha isy phly mujy kuch ni ata tha
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