Question

Explain 2d and 2.5d memory organization?

Answer 1

The main memory stores instructions and data of the currently executed programs. Usually, it is a random access memory RAM with reads and writes available. Sometimes, its part can be implemented as the fixed memory or read-only memory ROM.

Main memory with linear selection has a single address decoder used in a memory module. Information is stored in a matrix of data word locations.

In 2D main memory, the matrix is represented as a two-dimensional set of elementary bit locations. Each output line of the decoder selects (activates) a single word location. The elementary addressable location is a sequence of bit cells corresponding to a word. Thus, in this type of memory, we have a linear (direct) assignment of addresses and decoder outputs of word locations. To each bit cell belonging to the same word (elementary location) an output line of the address decoder is supplied and control lines which activate read or write in this location. To the inputs of the address decoder, the address bus of a processor is connected. The read/write signal is provided by the processor through the control bus. At the output of the memory cell matrix, a buffer register is placed connected to the external data bus of the processor. It stores the data read from the memory or those which are to be there written.

In 2.5D memory, the information bits read from the matrix are subject to further selection, which is a halfway in the direction towards a three-dimensional structure. in the main memory, the bit cells matrix is basically two-dimensional. The main memory in 2.5D memory is called as "Main memory with a linear selection of multiple words" and the structure of this type of main memory module is based on the memory with a single address decoder (linear selection). However, in this type of memory, each output line of address decoder activates not a single memory word cell but a sequence of memory word cells. After the readout from the memory matrix, these word sequences are introduced at inputs of a selector, i.e. a next selection unit that selects a single word out of them. During memory write, data from the data bus are directed to the proper word cell in the sequence selected by the address decoder. The address is divided into two parts: one selects a given sequence of locations and the other is supplied to the selector circuit. In the selector, the second part of the address is decoded and the output lines from the decoding select the memory locations to be used in the current memory operation.