Problem description:

What is the "bank" of memory, and how does it affect the use of memory?

Analysis:

Memory library is actually divided into two parts, logical library and physical library.

Let's talk about logical banks first. Inside the chip, the data in the memory is written in a large matrix in bits, and each cell is called a cell. As long as you specify a row first and then a column, you can accurately locate a cell, which is the basic principle of memory chip addressing. Such an array is called a logical bank of memory.

Let's talk about physical banks. Usually, each memory bank on the motherboard is divided into two sections, which can be easily inferred from the BANK 0/ 1 DRAM timing option in the BIOS settings of the VIA motherboard. In fact, there are two BANKs, but the concept of bank here is different from what we mentioned when analyzing the internal structure of the chip earlier.

Simply put, this BANK is the channel for exchanging data between the memory and the Northbridge chip on the motherboard. At present, taking SDRAM system as an example, the interface bit width between CPU and memory (that is, CPU to DIMM slot) is 64 bits, which means that CPU will send or read 64-bit data from memory at a time, so this 64-bit data * * * is a memory BANK, which is called Bank (physical bank) in the product descriptions of many manufacturers.

At present, most chipsets can only support one memory containing two physical banks. But for a specific stripe, many people take it for granted that each DIMM slot uses the number of memory chips to distinguish how many BANK channels are occupied. One side (16M, 64M) only occupies one physical bank, and two sides (32M, 128M) only occupy two physical banks. In fact, physical banks have nothing to do with the number of aircraft. PCB circuits can be designed as double-sided and single-sided, or all chips (16 chips) can be placed on one side (at least in theory).

Some memory chips are physical banks on one side, and some are physical banks on both sides, so we can't generalize. 256MB memory stick is a typical example. Although it is double-sided and has as many as 16 chips, it still belongs to a single physical bank. To accurately know the actual number of physical bars in a memory stick, we only need to know the number and bit width of logical bars of a single chip and the number of chips on the memory stick. The sum of the bit widths of each chip is 64, which is a single physical library. If it is 128, it is a dual physical library.

The relationship between CPU work and banks