I have a 3 years old ThinkCentre (A52, type 8381). It has 1GB of RAM in 4 256MB sticks. According to the model spec, it supports 400Mhz DDR2 memory. I would like to increase the amount of RAM I have, given how cheap 1-2GB sticks are today. However, someone told me faster memory sticks (say 800Mhz) cannot be used when only 400Mhz are supported. This is a bummer, because for some reason 1GB of 400Mhz DDR2 costs about 3-4 times more than a modern DDR2 stick with the same size. Is this really the case? Can't a memory stick work in a frequency lower than its optimal?
Can a 800Mhz memory stick be used in a 400Mhz slot
ddr2memorythinkcentre
Best Answer
The best way to check for compatible memory options is with Crucial's tool -- CrucialScan.exe
It has helped me on multiple old machines (workstations and laptops).
It will also answer your question accurately for your system motherboard capabilities.
For DDR2 PC2-xxxx and the MHz figures look at this DDR2 wikipedia page.
The two things are similar ways to measure almost the same thing.
Look at the Wikipedia table and small print under it.
PC2-5300 ~ 667Mtps ~ 333MHz
and,PC2-6400 ~ 800Mtps ~ 400MHz
.For normal things, either would not make too much of a difference.
If you get a price advantage, PC2-5300 would be fine.
Here is page-2 of a long article on Dual Channel memory discussing these details.
Further on your comments, people quote frequencies differently at times (probably to make life more confusing for the buyer).
There are a lot of other references that explain these terms.
Here is one more link which has these relevant lines after the explanation.