How Computers Work – Part 8 – RAM [Mega Series]
Today, we’re going to talk about the thing that makes your computer more than a simple calculator – random access memory (RAM). In an earlier part of this series, we went over the memory slots on the motherboard, but the simple description provided in that part isn’t sufficient to fully describe how RAM works. In the computing world, RAM can make or break your computer’s performance, sometimes more than the CPU.
What is RAM?
RAM, also known as physical memory, is essentially what stores everything open in your computer. It contains a repository of operating system libraries, drivers, open applications, and in some cases, rendering data for open windows. All the buttons in your program, every tab you open, and every video of Justin Bieber you click “Dislike” on is stored in memory until you close the Window it’s contained inside of.
How RAM Works
Just like the CPU, RAM stores all its memory inside a collection of transistors and capacitors. Read the CPU article if you have no idea what a transistor is.
If you aren’t familiar with capacitors, you only need to know that they store electrical energy and [generally] look like this:
Of course, the capacitors and transistors inside your RAM are much smaller and much simpler. Each capacitor in a RAM module stores a bit, the smallest possible increment of data in a computer. If you’re lost, read about bits and bytes first. If a computer wants to write a zero to a capacitor, it simply stops the flow of electricity to that particular capacitor by switching the transistor off.
There’s just one problem with this pretty picture of RAM: Capacitors can only store energy for a very limited amount of time. To counteract this, the memory controller on your motherboard “refreshes” the capacitors at a rate equivalent to the “memory clock,” which is very similar to a CPU clock.
The Big Picture
So, since you now understand the internal workings of RAM, you should also be aware that your computer writes anything you open to its capacitors. This stores only what’s running at the moment and cannot store anything permanently. When you install a program, it’s written to the hard drive. When you open the installed program, its contents and all data associated with it is written to memory so that the program runs.
Types of RAM
Once you understand how RAM works, and what RAM does, you’re ready to learn the most common types of RAM on computers:
FPM DRAM (Fast Page Mode Dynamic RAM) – This is probably one of the oldest types of RAM that existed in personal computers. It pinpointed every single bit of memory that the processor asked for, one at a time. Imagine how “fast” it would “page” things…
EDO DRAM (Extended Data-Out Dynamic RAM) – This type of RAM existed much later and used the same method of data retrieval as FPM DRAM, save for the fact that the module didn’t wait for each bit to be retrieved. It simply retrieved the next bit in the next clock cycle once the previous bit has been located.
SDRAM (Synchornous Dynamic RAM) - This type of RAM cycles through columns of data, assuming that the CPU will grab data in chunks instead of single bits, making it work faster than its predecessors. Most computers built during the late 90s implemented this type of doohickey.
DDR SDRAM (Double Data Rate Synchronous Dynamic RAM) - To understand this type of RAM, think of the memory clock as a heart beat. Every time the memory clock “beats” it has a diastolic and systolic rhythm – upbeat and downbeat. SDRAM only took advantage of the “downbeat” to retrieve data. DDR SDRAM, however, takes advantage of both the downbeat and the upbeat, making it twice as fast. This was improved further to yield DDR2 and DDR3 RAM.
RDRAM (Rambus DRAM) - A company named Rambus created a new type of RAM which works with a high-speed “Rambus” channel that helps accelerate the processing of read/write operations. Although not necessarily “better” than DDR SDRAM, it is worth a mention because the modules look cute. Oh, and the RAM modules tend to overheat, which is why they each need heat spreaders to help get rid of extra heat produced by massive electrical resistance.
VRAM (Video Memory) – This type of RAM usually exists in dedicated graphics cards for the sole purpose of storing rendering data and other things your computer would otherwise waste its own memory on. Although there’s many different forms of this RAM I prefer not to discuss, the important thing is that it has two different access ports: One for the CPU and one for a dedicated graphics processor known as the (GPU). It makes graphically intense applications run much more smoothly.