Parallel storage structure

One 、 Parallel storage structure

Used to improve memory access speed , It includes the following two categories ：

1.   Double port RAM

2.   Multi module memory ; Single multi word  、 Multibody parallel

Two 、 Double port RAM：

Concept ：

• Two groups of independent read / write control circuits and two read / write ports are provided in one memory , It can provide parallel reading and writing of two data at the same time .

purpose ：

1. General register group  ;
2. Instruction prefetch unit , It's like a queue , Put instructions in the queue ahead of time ;
3. CPU And other processors

3、 ... and 、 Multi module memory

Single multiword system

• That is, a storage bank , Increase memory word length W—>4*W; Each access cycle ,CPU Take a word from memory W, After increasing the word length , One access cycle can take one word 4W, It is equivalent to increasing the access speed .

shortcoming ：

• Anaphora conflict , Mainly transfer instructions ; Take out continuously 4*W, Four instructions , If it is jump when the first item is executed , And is an instruction that jumps to the next fetch , This will result in the waste of three instructions for this fetch .
•   Read operand conflict , The required operand is not in the storage word for a single fetch
•   Write data conflict , Need to gather 4W Can be written once , If you need to rewrite one of them W The data of , Need to be continuous 4W Read, modify, and then write .

  Multi body parallel system

Concept ： The memory is composed of a plurality of memory banks , Each bank has the same capacity and speed .

Each bank can work independently , There is a separate data address register 、 Address decoding 、 Drive circuit 、 Read write circuits .

According to the addressing order ：

    a. High cross , Sequential addressing ;
First make up an individual , Make up another one ;
The access address consists of ： Body number + Body address ;
    b. Low cross
Make up each body first 0 Address , Again 1 Number , Down in turn ;
The access address consists of ： Body address + Body number
Increase memory bandwidth , That is, multiple banks work at the same time