If you’ve been around computers for a while, you have probably had someone ask what the memory in the computer does – exactly. Maybe you artfully spoke of the RAM’s ability to access memory randomly, hence its name, Random Access Memory. Maybe you twisted in your chair and regaled the heroics of RAM inside the computer’s framework, describing in detail how it receives orders from the CPU, finds data based on rows and columns, and returns that information much faster than many other types of memory. Maybe you spoke of RAM’s volatile nature – in other words, how it doesn’t store anything with the power off. Maybe you spoke of pushing the computer’s power button to start the computer’s RAM from a clean slate. This article explains RAM and its most dominant form in today’s computers – DRAM.

RAM stands for Random Access Memory. The randomness is what sets this type of memory apart from, say, tape drives or CDs. A request for data can come in at any point and the memory can access it at the same speed as other bits of data, unlike CDs or tape drives which require you to move to different locations on the media to find the data. RAM is therefore fast, reliable, and perfect for developers working on computer systems.

When powering on a computer, the RAM really takes on its life. The memory modules in a desktop or notebook receive address requests from the CPU. If that address doesn’t exist in the memory module, then the module must flush a row of memory, request a new row, wait for it to become active, and then request the column in the row. The column is accessed and the data comes pouring in from the memory bus. The data isn’t sent like you would imagine. It’s actually sent in bursts that are appropriately named burst lengths. The burst length of a memory module depends upon its physical length and number of columns. But are we getting ahead of ourselves?

How Does RAM Fit into a Computer’s Makeup?

RAM can actually refer to many different types of memory inside a computer system, including the “CPU registers, on-die SRAM caches, external caches, DRAM, paging systems, and virtual memory or swap space on a hard drive.” (Source: Wikipedia.org) In this article we’ll focus mostly on the DRAM modules inside the computer. While understanding the Dynamic Random Access Memory modules, a person can come to understand most applications of memory inside a computer.

There may be those among us who don’t quite get RAM’s purpose in a computer. For you, I’ll try a metaphor. Most of us working stiffs have offices where we have a filing cabinet and workspace. In our metaphor, the cabinet would be the hard drive and the workspace would be the RAM. On our workspace we would spread out our tools to complete our project. The tools we spread out would be made available through the RAM, not the hard drive. The hard drive’s speed prevents it from offering up the tools the CPU needs to perform a task. The drive must spin up, access the data on the file system, and send it back to the CPU. The RAM, on the other hand, can store information quickly, have it readily available for when the CPU needs it, and do it all very quickly. Just like the workspace in our metaphor, the RAM’s usefulness depends on how much space is available and how fast it can work.