What Is The Difference Between DDR2 & DDR3 RAM

RAM,or Random Access Memory, is your computer’s short term memory. If your computer needs information and does not find the RAM, it then needs to journey to the hard drive to try and retrieve the data, which is far more time consuming. Many older computers that feel sluggish can be given new life if upgraded with additional RAM.

However, capacity is only one specification. RAM is also available in a variety of versions and speeds. A 2GB stick of DDR2 800 RAM is not the same thing as a 2GB stick of DDR3 1333 RAM. Understanding the difference is important because computers will generally accept only certain types of RAM.

Let’s take a look at the different types of DDR memory on the market and how they are different from each other.

The Big Issue: DDR2 vs DDR3

In late 2008, Intel released the first Core i7 processors. These processors were paired with a new motherboard chipset called X58. This chipset introduced the need for a new type of memory called DDR3.

In the last two years the entire industry has converted over to DDR3. All of Intel’s new processors can only be used with a motherboard that requires DDR3. Recent AMD motherboards are also changing over to DDR3.

The term “DDR” stands for Double Data Rate RAM. This term came into use at the turn of the century when the first Double Data Rate RAM modules arrived. Double Data Rate RAM was capable of two data transfers per clock cycle, giving it twice the theoretical peak bandwidth of previous SDRAM while running at the same clock speed.

DDR2 and DDR3 are improvements on the same technology and further increase the number of data transfers per clock cycle. DDR2 RAM provides 4 data transfers per cycle, while DDR3 increases the number to 8. Assuming a base clock speed of 100Mhz, DDR RAM will provide 1600 MB/s of Bandwidth, DDR2 provides 3200 MB/s, and DDR3 provides 6400 MB/s. More is always better!

Performance & Compatibility Consequences

Does this mean you’ll notice a big difference between DDR2 and DDR3 systems? Well, maybe not. While the increase in memory bandwidth is great, the truth is that 99% of programs are not capable of creating a workload that will be restricted by memory bandwidth. The issue is most relevant to server and workstation class products.

To see a difference in performance you’ll usually need to use a benchmark program capable of testing memory bandwidth.

However, purchasing DDR2 or DDR3 RAM isn’t usually a matter of preference. DDR2 and DDR3 RAM are not compatible. If your motherboard uses DDR2, you cannot upgrade to DDR3 without upgrading your motherboard. This means that if you currently own a computer with DDR2 RAM and you want to upgrade to a brand new processor and motherboard you have to throw your your perfectly good DDR2 RAM and buy new DDR3 RAM.

There are a few motherboards which are exceptions to this rule, but they are exceptions only because they provide both DDR2 and DDR3 RAM slots, and these exceptions are available only on older chipsets.

I know – it’s a bummer, but there isn’t much you can do about it. Both Intel and AMD have committed to DDR3 RAM for future products, so you’ll be forced to either buy new RAM and deal with your computer becoming a dinosaur.

Clock Speed – The Other Part Of The Equation

Another important specification to consider when looking at RAM is the clock speed. Clock speed is an indication of how well the RAM will perform in much the same way that clock speed indicates how well a processor will perform, and it is part of the equation that determines the maximum theoretical peak bandwidth of memory. A higher clock speed is better. However, as I mentioned previously, this is a difference that is unlikely to be noticeable in normal daily use. The typical enthusiast won’t see much benefit from memory with a higher clock speed.

With that said, there are motherboards that only accept memory within a limited range of clock speeds. It is always a good idea to consult a motherboard manufacturer’s website to double-check the RAM that is compatible. Motherboards are usually very flexible in this regard, but it is better to be safe than sorry.

Conclusion

The bad news is that the invention of DDR3 is making DDR2 obsolete by force. I have four sticks of spare DDR2 memory that are no longer capable of finding a home in a new system, even a low-power HTPC or office computer, because of the change. The good news is that new RAM technology is at least several years off, so DDR3 purchased today should be good for a while. Just be sure to check the type of RAM a new motherboard requires before purchasing RAM to go with it!