This lesson will help you answer the question, ‘What is primary storage?’ It will help you understand how primary storage works in your computer, the devices that comprise primary storage, and the different types of primary storage.
What is Primary Storage?
Have you heard these terms: primary storage, main storage, primary memory, or internal memory? Have you wondered what each of them means? All of these terms may seem like a lot to learn and may have you thinking that computers are impossible to understand, but don’t let yourself become overwhelmed, because those are all terms for the same thing: RAM, or random access memory.
When many people hear the term ‘primary storage,’ they think of the hard drive on the computer — where you store or save your data. But primary storage is actually where the data you are actively using is being stored. In other words, whatever you are working on at the moment is being held in primary storage.
Relationship Between RAM and CPU
The device you’re using when actively working on your computer is the RAM. The RAM is the only storage that has direct access to the central processing unit (CPU), or the brains of your computer, through what is called a bus.
A bus is a pathway or circuit that allows the RAM to communicate directly with the CPU to complete the tasks you want accomplished.That sounds complicated, but what does it really mean? Let’s say you arrive at school carrying your book bag and sit down at your empty desk. The empty desk is the RAM, or primary memory. As you get ready to study, you take items out of your book bag and place them on the desk. The desk gives you the space you need to get down to business and use your items, such as pencils, folders and books.
Just like RAM, the desk serves as the workspace you need to accomplish tasks.The down side of RAM is that it is volatile. If something happens — say, your computer suddenly shuts down — anything that is stored there is lost. This is why you are constantly told to save your work often — once you save the work from RAM into something more permanent (like your hard drive or a portable storage device), you don’t have to worry about losing your work.
Exploring the Role of Cache Memory
Another part of RAM is known as the cache. This is a form of primary memory that is directly attached to the CPU; there is no bus or pathway from the CPU to cache memory. It helps to make your computer even faster since it is right there next to the CPU.
If we were to draw a picture of the CPU, RAM, and cache, here is what it would look like:
Notice how the cache is directly attached to the CPU? This makes communication between the cache and CPU super fast. The arrow connecting the CPU to the RAM, or primary storage, is the bus — it provides a transportation route for data to go between the CPU and RAM. Other memory (like secondary or tertiary) does not have this direct access or route to the CPU.
Sequential versus Random Access
Let’s talk about random access. The term refers to how your CPU locates information in your working space — it can jump from point to point to go directly to the piece that it needs.
This is important because years ago when computers first had storage it was accessed sequentially; in order to find a piece of data, the CPU had to go through the storage from slot 1 through slot 100. Think of it like a bank of post office boxes — if you had to pick your mail from box 39 sequentially, you would have to look in box 1, then box 2, then box 3, and 4, 5, 6, etc.With random access, you can go directly to box #39 and retrieve your mail. Random access makes it so much faster for your CPU to be able to retrieve the programs you want to work on and make their tools available to you.
Types of RAM
There are a variety of types of RAM. Let’s talk about some of the types you might see when you are shopping in a computer store:Dynamic random access memory (DRAM): This is the memory for most PCs, laptops, and video game consoles. It is the simplest in that it contains a storage unit for each bit of data — the storage unit is either full (1) or not (0).
It must be refreshed periodically or it will leak its data. DRAM is asynchronous, which means it responds to commands as they are made without worrying about the clock or pulse of the CPU.Synchronized dynamic random access memory (SDRAM): SDRAM uses the computer’s clock or normal pulse to control its access to the CPU. SDRAM only pushes forward commands in time with the computer’s internal clock — this actually makes it faster than DRAM since the computer’s internal pulse happens automatically and very rapidly.Static random access memory (SRAM): SRAM uses a lot of power and is much faster than DRAM. However, keep in mind that SRAM is not generally used for working memory or primary storage.
Whether you’re talking about primary storage, main storage, primary memory, internal memory, or RAM, you are talking about the workspace your computer has available to perform the tasks you are asking it to do.
RAM communicates directly with the brains of the computer, the CPU, so that your tasks are accomplished as quickly as possible. While both synchronized dynamic random access memory (SDRAM) and dynamic random access memory (DRAM) are found in laptops and PCs, DRAM is the most commonly used. So, if you are looking to increase the amount of primary storage you have available to work with, chances are you will be looking for DRAM.