Data Storage - (Main|Physical) Memory - Random-access memory (RAM)

1 - About

memory in a hardware context.

RAM (Random-access memory) - known also as:

  • main
  • or physical memory

Physical memory is the DRAM memory installed on the host.

It is a memory storage device which:

  • is volatile
  • have some noticeable latency access
  • have a significant larger capacity

The word RAM is often associated with volatile types of memory (such as DRAM memory modules), where the information is lost after the power is switched off.

Today, it takes the form of integrated circuits that allow stored data to be accessed in any order (i.e., at random access). “Random” refers to the idea that any piece of data can be returned in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data. By contrast, storage devices such as magnetic discs and optical discs rely on the physical movement of the recording medium or a reading head. In these devices, the movement takes longer than data transfer, and the retrieval time varies based on the physical location of the next item.

3 - RAM Architecture

where:

  • the memory controller is a primitive processor that can quickly find addresses and copy information stored in the addresses to/from the system bus. This works faster than if the processor did the work of reaching into storage to extract information.

4 - DDR3

In computing, DDR3 SDRAM means double-data-rate three synchronous dynamic random access memory and is a random access memory.

4.1 - Transfer rate

With data being transferred 64 bits at a time per memory module, DDR3 SDRAM gives a transfer rate of

<MATH> \frac{(\text{memory clock rate}) × 4 (\text{for bus clock multiplier} × 2 (\text{for data rate}) × 64 (\text{number of bits transferred})}{ 8 (\text{number of bits per byte}) } </MATH>

Thus with a memory clock frequency of 100 MHz, DDR3 SDRAM gives a maximum transfer rate of 6400 MB/s.

5 - Documentation / Reference

data_storage/ram.txt · Last modified: 2018/09/22 17:20 by gerardnico