Associative Memory

What is associative Memory?

• Associative memory looks for data by the value of the data rather than by an address. This form of search dramatically reduces the amount of time it takes to find anything.
• "The memory is referred to as associative memory or content addressable memory when data is accessible by data content rather than data address."
• जब डेटा को डेटा एड्रेस के बजाय डेटा कंटेंट द्वारा एक्सेस किया जाता है, तो मेमोरी को एसोसिएटिव मेमोरी या कंटेंट एड्रेसेबल मेमोरी के रूप में जाना जाता है।

How associative memory works? 

The following is a list of stages that illustrate how associative memory works in computer architecture.

1. Data is saved in the first available empty memory location.
2. When data is stored in associative memory at a specific place, no address is saved with it.
3. When searching for stored data, just the key (i.e. data or a portion of data) is supplied.
4. To identify the matching key from the memory, a sequential search is done in the memory using the supplied key.
5. If the data content is found, the memory stores it for future reading.

Associative memory organization

The hardware structure for associative memory is made up of the following components:

• Memory Array.
• Logic for m words with n bits per word.
• Several registers like input register, mask register, select register and output register.

The following is a block diagram explaining how associative memory is organized:

Associative Memory

Functions of the registers used in associative memory is given.

• Input Register (I)- The data to be written into the associative memory is stored in the Input Register (I). It's also where you keep the info you're looking for. It can retain data containing one word of length at any one moment (say n).
• Mask Register (M)- The Mask Register (M) is used to provide a mask for selecting a key or specific field in the word of the input register. The maximum length of the mask register can be n since the input register can carry data of one word of length n.
• Select Register (S)- Each memory word is represented by one bit in the Select Register (S). When the input data in I register is compared to the key in m register and a match is discovered, the bit in choose register is set to that value.
• Output Register (Y)- The matched data word from associative memory is stored in the Output Register (Y).

Associative memory's benefits

• The search for associative memory is quick.
• Parallel searches benefit from associative memory.

Associative memory's drawbacks

• RAM is less costly than associative memory.