Hardware - memory upgrade question

I am thinking of upgrading my memory to 4GB....
These are the chips available:


Does anyone know what the difference is between the 667MHZ and 800MHZ? Does it depend on my machine?
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Aztec ComputersConnect With a Mentor Commented:

It will depend on the fsb bus of your machine's motherboard. I would use the crucial memory scanner to find the best memory upgrade as it scans your hardware and then gives you results based on your own machine:

Hay, well the real difference between the two are its speed of read. 1hz=1 operation. So the more the marrier when it comes to HZ on RAM. The issue here is that the older the motherboards the less HZ can the bus read. So you need to figure out what HZ your motherboard can carry and then go for that.
go for the 800 mhz it faster and more standard than the 667 mhz and if it compabile with our dell by all means go for it.
Dell computers can be picky with there ram upgrades.

It actually depends on your cpu - the cpu determines what FSB your motherboard sets, if it is able to handle both.  That being said, both DDR2-667 and DDR2-800 are fast enough for what current Core2 cpus run at.  An E8400 with a 1333FSB actually runs on a motherboard FSB of 333, which means DDR2-667 will do the job.  I would suggest using only two modules, as four may present too much of an electrical load and possibly slow down the system to compensate or crash completely.
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