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Interleaved memory.

The memory system in which successive addresses are evenly spread across memory bank to compensate for the relatively slow speed of DRAM.

The contagious memory reads and writes are using each bank in term, resulting in higher memory throughputs due to reduced waiting for memory banks to become ready for desired operations.

Types of Interleaving:

1. Low order Inter leaving.

In this lower order address lines eg. A0-A12 used to identify location in each bank whereas higher order address lines are decoded to generate chip select (CS) of individual memory chip. In this low order interleaving successive address will get allocated in the same memory chip as shown below.

Here in this low order interleave memory even if contagious addresses generated by CPU it will be allowed byte by byte transfer.

2. High order Interleaving.

In this case higher order address lines, eg, A3 - A15 used to identify location in each bank where as lower order address lines eg. A0, A1, A2 will be decoded to generate CS 07 individual chip. This will allocate successive addresses in the different memory bank as shown below.

In above high order interleaved memory it can be possible to read and write 8 data words simultaneously and have data transfer speed is comparative faster.

3. Associate memory (CAM).

This memory is also known as content addressable memory. Its hardware organization consist of argument register to hold CPU's request & a key register to hold predefined "mask" which is logically 'AND'ed with the CPU's request in argument register. The result of CPU's request will be masked and remaining unmasked bits are then parallel y searched against each word in the associative memory array as shown below.

During this parallel search as soon as the match is found the corresponding match register bit will be set and the data word from this matched location is placed on the OUTPUT for CPU.

The associative memory finds an application where search time is critical and very short. For example, directory search in the computer or website search in the internet system makes used of associative memory.

In this associative memory if the matched words are contagious the will be placed on OUTPUT, one after another without any intermediate gap as a result the data transfer rate will be very FAST for the associative memory.