Difference between DDR2 vs DDR3 RAM

If your computer was built in 2008 or earlier, then chances are that it has the older DDR2 RAM instead.

At buildcomputers.net, we don't take chances or make guesses. so let's learn what are the differences between DDR3 vs DDR2 RAM and how to tell them apart.

How to Tell If You Have a DDR2 or DDR3 RAM Module

In terms of physical appearance, DDR2 vs DDR3 RAM looks largely similar. They are of the same length (

13.3 cm or 5.25 in) and have the same number of pins (240):

Here's the trick to tell them apart: Look at their notch positions (circled in yellow above).

As you can see from the image below, the DDR2 notch is located near the middle of the RAM stick while the DDR3 notch is positioned nearer to the left side. If you want to be more precise,

  • DDR2: distance between left side of RAM stick and notch = 7.1 cm (2.8 in)
  • DDR3: distance between left side of RAM stick and notch = 5.4 cm (2.1 in)

This difference in notch position is also why you can't use DDR3 RAM in a DDR2 system or install DDR2 RAM into a DDR3 slot (even though they have the same number of pins).

In short, DDR2 and DDR3 RAM are not compatible with each other: If your motherboard has DDR2 RAM slots, then you can only use DDR2 RAM. The same applies to DDR3 RAM.

What's the Difference between DDR2 and DDR3 RAM?

Number of Pins
Clock Speed
Max Transfer Rate

240 pins
400 to 1,066 MHz
3,200 to 8,533 MB/s

240 pins
800 to 2,133 MHz
6,400 to 17,067 MB/s

Can I replace a DDR2 RAM module with a DDR3 module?

The computer is a Compaq Presario CQ40. It currently has 1 GB of RAM DDR2 (Samsung-manufactured). There are two slots in the RAM part.

It says 766 MB usable ( which I think is because part of it goes to being the graphics card). The processor is an AMD Sempron(tm) SI-42 2.10 GHz.

I wanted to upgrade the RAM to 2 GB with a new installation of one 1 GB RAM, but I was also wondering if I can replace the old 1 GB DDR2 with a new 2 GB DDR3 RAM, and add

one more 1 GB DDR3 RAM, making the whole RAM capacity to 4 GB DDR3.

Please give me some thoughts. I think there have to be compatibility between the

motherboard and the new planned DDR3 RAMs as well, which I am not sure how to check.

According to Crucial you can upgrade your laptop either to 4GB or to 8GB, depending on the exact model. I suggest you head over to Crucial's site (crucial.com in the US, crucial.com/uk in hte UK, and I'm sure there are other local versions) and run the "system scanner" which will identify your model accurately, and will take you to a page showing you all the upgrade options available (available from them, that is, but they have a fairly comprehensive stock of memory modules).

1) 2 SODIMM slots

2) Supports up to 4 GB of system RAM

3) PC2-6400 800-MHz, DDR2

4) Supports the following configurations:

? 4096 MB total system memory (2048 ? 2)

? 3072 MB total system memory (2048 + 1024)

? 2048 MB total system memory (2048 ? 1)

? 2048 MB total system memory (1024 ? 2)

? 1024 MB total system memory (1024 ? 1)

if you change to DDR3 you will have problems

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How To Identify Different Types Of Computer RAM

RAM is one of the most important parts for a computer and people usually get confused with its types. So, today I am going to tell you how to identify DDR1, DDR2, DDR3 and DDR4 computer RAM. You can identify a DDR1, DDR2, DDR3 and DDR 4 RAM on Windows and Mac or by doing a physical examination.

How To Identify DDR1, DDR2, DDR3 And DDR4 RAM Physically

DDR1, DDR2, DDR3 and DDR4 RAM are mostly used in the market. However, DDR 1 and DDR 2 are hard too find nowadays but, if you find any here is how you can identify it.

First, keep your RAM front-facing as you can see in the image below. Just, take a look to the notch each DDR cut out or notch distance is different from others DDR. You can see it in the image.

1. Distance of Notch

A notch means a little cut out mark between the pins of a RAM.

  • DDR1, DDR2, DDR3 and DDR 4 all of them have a cut-out mark on the base of the RAM.
  • But you can see the cut-out mark or notch distance easily.
  • Notch of DDR1 and DDR2 RAM are quite similar but if take a closer look.
  • You can find DDR1 notch right underneath the IC (Integrated Chip) and DDR2 notch is a bit far from the IC.
  • Notch of DDR3 is different from the other two.
  • Notch of DDR4 is almost in the middle and right underneath the IC.

2. Integrated Chip (IC)

  • DDR3 RAM has a small and square type IC.
  • DDR2 RAM IC is bigger than DDR3 but, its smaller than DDR1.
  • IC in DDR1 touches both the top and bottom of the RAM.
  • The IC in DDR2 RAM is in the centre.
  • DDR 4 RAM also has small and square type IC like DDR 3 but, in two rows.

3. Number of Pins in DDR1, DDR2, DDR3 and DDR4

  • A DDR1 RAM contains 184 Pins.
  • A DDR2 RAM contains 240 Pins.
  • A DDR3 RAM contains 240 Pins.
  • A DDR4 RAM contains 288 Pins.

4. Voltage of RAM

The voltage of RAM cannot be used to physically identify any RAM. But, it can be very helpful when you place a RAM in the motherboard slot because the voltage is written on the RAM slot of the motherboard.

  • DDR1 RAM operates at a voltage of 2.5 V.
  • DDR2 RAM operates at a voltage of 1.8 V.
  • DDR3 RAM operates at a voltage of 1.5 V.
  • DDR4 RAM operates at a voltage of 1.2 V.

How To Identify DDR1, DDR2, DDR3 And DDR4 RAM On Windows

First, launch the Task Manager on your PC and click on the Performance Tab. Now, select memory option from the left column, and look at the very top right. It will show how much RAM you have and on what type of RAM your is using. You can see in the image below, that my system is running DDR3.

How To Identify Different Types Of RAM On Mac

A quick way to see what type of RAM is installed in your Mac. Look at the top left corner of your screen, you will see an Apple icon click on it. Now, go to About this Mac Under Overview Memory and it will show the information about the RAM.

So, this is how you can identify different types of RAM on Windows and Mac or doing a physical examination. Do let us know in the comments box which method works for you, and share it with your friends.

How to Differ DDR3 from DDR2 Memory

The most obvious factor on how to differ DDR3 from DDR2 memory is appearance. But, that is not as simple as it might seem. Unless you can find the specific reference on the memory stick, you will need to look at the key notch. Along the bottom of the memory stick, 240 pins insert into the motherboard. Among the pins is a notch. That notch prevents inserting the wrong type of memory into an incompatible slot. Looking from the top side, the notch on the DDR2 lies slightly to the right of the middle point of the memory stick. On the DDR3, the notch is slightly to the left of the middle.

DDR2 memory sticks do not fit into the slots for DDR3 sticks or vice versa. One reason why many manufacturers have been slow to adopt the newer DDR3 technology is because there is no backwards compatibility between the two. You cannot use a DDR3 when you do not have an appropriate slot in the motherboard for it. Some newer motherboards come with the ability for both types of memory to work. However, it is important to know how to differ DDR3 from DDR2 memory before you purchase it.

What else makes these memory sticks different? Transfer speed on DDR3 is double that of the DDR2. Transfer rates on DDR2 range from 400 to 800 Mbps. On the DDR3, the range is 800 to 1600 Mbps. The DDR2 has four internal banks of memory while the DDR3 has eight. The DDR2 does 4-bit prefetch and the DDR3 does 8-bit prefetch. The DDR2 uses more voltage than the DDR3 does. The DDR2 runs with 1.8V while DDR3 runs with 1.5V. DDR3 memory has a slightly higher latency than the DDR2. There are other technical differences between the two as well.

Currently, there is another significant way on how to differ DDR3 from DDR2 memory. The price is higher for the DDR3 memory sticks. Prices have continued to drop ever since the DDR3 came on the market a few years ago. However, the DDR2 sticks are still lower in price. But, newer motherboards are pushing the prices down on DDR3. The demand for the newer technology is starting to grow as higher memory requirements come into play with faster motherboards and chipsets. However, with the newer DDR4 technology planned for a 2012 release, the future of the DDR3 is still in question.

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