How Can We Recognize DDR1 and DDR2 RAM?

by Tina Gasperson

Q: How can we recognize DDR1 and DDR2 RAM? — Alim

The two types of RAM modules are similar in their appearance, but don’t get them mixed up because they are most definitely not interchangeable. If you accidentally purchase the wrong kind of RAM, it won’t even fit into your computer – and you’ll be heading back to the store.

DDR RAM is the most frequently used RAM module in today’s computer systems. There have been many different types of RAM, but don’t get confused – just remember DDR RAM or DDR2 RAM and chances are you’ll be safe. If you have a laptop, then the smaller SODIMM DDR RAM or SODIMM DDR2 RAM is what you’re looking for. Let’s look at the visual differences between these.

DDR1 RAM, also known as simply DDR RAM, has 184 pins that fit into the slot intended for it inside your computer on your motherboard. DDR2 RAM has 240 pins, and a notch at the bottom that is in a different location than the notch on DDR RAM. If you try to install DDR in a motherboard that is built for DDR2, or vice versa, you won’t be able to coax it into place, and even if you could it wouldn’t work.

For those of you with laptops, a smaller RAM module with the same computing power is available. These smaller modules are called SODIMMs and are available in DDR and DDR2 format. Both DDR and DDR2 SODIMMs have 200 pins, but alas, they are still not interchangeable. The DDR SODIMM has an off-center notch at the bottom, and the DDR2 SODIMM has a notch that is right about in the center. These notches are meant to prevent mis-installation, but that hasn’t prevented many a determined newbie from forcing the RAM module into a slot that wasn’t meant for it. If you do this, you’ll break either the RAM module or the motherboard slot, or both. To prevent this kind of error, take your old RAM module with you to the store and match it up exactly to whatever you’re thinking of buying.

Tina Gasperson (tinahdee@gmail.com), affectionately known as Computer Lady by her family, has been writing about IT, home computing, and the Internet for more than a decade.