I would like to upgrade my Lenovo ThinkPad X100e with more RAM.  It originally shipped with 1GB of memory.  What size memory modules will work with my X100e, and can I use 800MHz memory modules in place of the 667MHz it shipped with?  If so, will this improve performance?

Also, should I add one 2GB module for a total of 3GB intsalled,  or should I go to 4GB under Windows 7?

For best results, you should use memory with the following characteristics:

• PC2-5300 DDR2 SDRAM 667MHz SO-DIMM Memory

Faster memory can be installed, however, it will be limited to this speed.

The ThinkPad X100e has a total of two memory expansion slots for SO-DIMM memory modules, one of which is occupied by either a 1GB or a 2GB SO-DIMM memory module.  Since one slot is already filled, installing one additional 2GB SO-DIMM memory module will increase the amount of memory in your X100e to either 3GB (1GB+2GB) or 4GB (2GB+2GB).

If your ThinkPad X100e has 1GB installed and you wish to increase the amount of installed memory to 4GB, then you will need to remove the currently-installed 1GB memory module and install two 2GB SO-DIMM memory modules, for a total of 4GB of RAM.

If your ThinkPad X100e has 2GB installed and you wish to increase the amount of installed memory to 4GB, then you will need to install one 2GB SO-DIMM memory modules, for a total of 4GB of RAM.

NOTE:  For best results when upgrading from 2GB to 4GB of RAM, you should use a memory module with the same speed and characteristics as the currently-installed 2GB SO-DIMM.

If you are running a 32-bit operating system, the X100e will only recognize about 3GB of RAM, so upgrading a 1GB system to 3GB by adding a 2GB module may make more sense.  If you are running a 64-bit operating system (or plan to upgrade to one in the future), going to 4GB of RAM (or more) will help impove performance.

An 8GB memory configuration using two 4GB memory modules has been reported to work well in a ThinkPad X100e running a 64-bit edition of Microsoft Windows 7.  The characteristics of the memory modules are as follows:

• 8GB (G.SKILL G2-6400CL6D-8GBSQ with two 4GB DDR2-800 PC2-6400 CL6-6-618 SO-DIMMs)

Note that while memory that operated at a frequency of 800MHz was installed, the X100e could only access it at a slower speed:

For a detailed step-by-step guide to replacing the memory modules inside a ThinkPad X100e, you can watch Lenovo's own service and support training videos for the Lenovo ThinkPad X100e Notebook (Adobe Flash required to view this website).  In the left menu pane, select CRU Removals/Replacements section and then view the video beneath it titled DIMMs.

NOTE:  A small Phillips screwdriver is required to loosen the seven (7) screws attaching the bottom cover to the ThinkPad X100e.  The screws themselves are held in place and remain attached to the bottom cover.