CompTIA A+® Certification All-In-One For Dummies®, 2nd Edition

3.2. Identifying the Types of DRAM

DRAM is the most popular type of memory used in systems today. It is also the most popular type of memory that computer users add to their computers when upgrading memory. Therefore, you must understand the different types of DRAM and what types of DRAM outperform others.

3.2.1. Standard DRAM

Memory is organized into rows and columns, like a spreadsheet. Information is stored in the different cells, or blocks, that are created by the intersection of these rows and columns. With standard DRAM, the CPU requests data from the memory controller by sending the address of the row and the address of the column for every block of data that needs to be read. The memory controller then fetches the information from that memory location. Figure 3-1 shows two memory cells that hold data that the CPU wants to have.

Figure 3.1. Looking at how data is accessed in memory.

To access the information shown in Figure 3-1, the CPU follows these basic steps to request information from standard DRAM:

1. In the first clock cycle, it sends the row address (1).

2. In the second clock cycle, it sends the column address (2).

3. On the third clock cycle, the memory controller reads the information (Address 1-2).

4. In the fourth clock cycle, the row address for the second memory cell is given (1).

5. In the fifth clock cycle, the column address for the second memory cell is given (4).

6. In the ...