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Posted: December 8, 2005
Written By: Dan "Tweak Monkey" Kennedy
The advice contained in this article is free for use at your own risk. If you can't benefit from this article, please pass it on to someone who can and view our other articles. For technical support, visit the Tweak3D Forums.
Which RAM Should You Buy?
Before you go shopping for RAM, you need to answer three questions.
1) How many free slots does the notebook have?
2) What size (and how many) sticks are needed?
3) What speed memory does the notebook require?
Almost every notebook has two memory slots. To save money, manufacturers will often use two smaller sticks to make up your total memory. For example notebooks with 256 MB RAM often have 2 x 128 MB sticks instead of a single 256 MB. In this case, adding an additional 256 MB to your 256 MB notebook will only bump your memory to 384 MB, since a single 128 MB stick must be removed to install the new memory.
You will need to check to see if there are open slots by removing the memory cover from the bottom side of the notebook. Shut it down and flip it over. Remove the memory cover on the bottom side of the notebook (it is probably held in place with either 1 or 2 small philips head screws). This process is covered in detail on page 4.
You can also download a program such as BTN Inventory IP to tell you how many free slots you have.
Some notebooks have the second memory stick behind the keyboard, on the opposite side of the case. Upgrading the memory in this slot is much more difficult and the topic will be saved for a future article. If you have to disassemble the notebook, check Google or the manufacturer's web site for instructions. Hopefully if you run into this today your free slot is on the closer side!
What Size Stick(s) Are Needed?
Now that you know the number of free slots, you can figure out what size memory you'll add to your notebook. This is easy to determine. Simply subtract your desired total memory from the useable sticks, if any.
Example - You want 512 MB in a notebook that currently has 256 MB (in two 128 MB sticks). In this case you must remove one 128 MB stick and replace it with a 512 MB, giving 640 MB. Or you can remove both and add two 256 MB sticks, though this tends to cost more and limits upgrade paths in the future.
What Speed RAM to Buy
You must determine what speed is required for the memory you're buying. The "configurators" on PNY or Kingston's site can help figure this out for you. As a rule of thumb, less than 900 MHz = PC100, less than 1.3 GHz = PC133 and if it's faster and newer it'll probably require PC2700+. On newer models, be sure to confirm if it requires DDR2 or not! Check the manual, manufacturer's web site, or the configurators linked above for details.
DDR2, which can operate in dual-channel mode, doubles the theoretical memory bandwidth. If your notebook supports DDR2, you may want to match the memory sticks with same brand, speed, and size (e.g. 2 x Kingston 256 MB DDR2 PC3200). DDR2 is currently somewhat rare and is typically only on newer, higher-end notebooks. It can still operate in single-channel mode, which is marginally slower.