RAM Upgrade, looking for some help

Hey, I'm familiar with computer workings for the most part except when it comes to RAM. Currently, I have 3GB DDR2 PC6400 RAM (2 Dimm (1GB + 2GB)).

I'd like to upgrade to 4 GB to support W7 64bit better.

From what I understand, the terms PC6400 and 800mhz are interchangeable for the most part. Meaning that it's 8 bit x 800 = 6400. So at this point, I'm assuming that when the Crucial.com scan tells me I my computer supports DDR2 PC6400/PC5300, it's safe to assume that my computer supports DDR2 800, correct?

Some things are throwing me off, however. I'm worried about bottle necks in my comp and was looking through CPU-Z and picked out some numbers that may have some relation:

DRAM Freq: 400mhz (I'm assuming that since I have DDR, that this number is doubled? Please correct me if I'm wrong)

CPU:
Bus Speed 266mhz
Rated FSB 1026mhz

Pertaining to the last two above, I seem to recall hearing somebody say that your RAM speed can only be as high as a certain speed pertaining to either Bus Speed or FSB, these terms are getting jumbled in my head.

With the thought that my computer can run DDR2 800 just fine, I found 2 possible choices from newegg:
http://www.newegg.com/Product/Product.aspx?Item=N82E16820227251
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231156
What do you guys think?

 

800MHz DDR2 will work just fine. You don't need 2 x 2GB. One of your memory sticks should already be 2GB; just swap out the other DIMM for a 2GB DIMM.

 

Thank you for the reply. You brought up a good point that I also am confused about. I have dual-channel support, so wouldn't it be best to get 2 DIMMs of the same type including clocks? My current RAM is 6-6-6-18 and the newegg ones are 5-5-5-5. Again, I hardly have any idea what I'm talking about, I'm just looking at numbers and trying to make sense of it.

 

You don't need identical DIMMs to run dual channel. You just need two DIMMs. There will be a small performance penalty for running asymmetric dual channel, but you won't notice it at all.

 

your computer will support DDR2-800 ram and if you want dual channel , just get another 2GB RAM stick just like i did.

 

The two dimms would run at the same frequency and timings though, so it would be completely symmetric. The bios will read the timing tables from each dimm and automatically set itself to the slowest one. Asymmetric (quasi)dual channel only happens with dimms of different sizes. In this case, if he buys a dimm with 5-5-5-15 major timings, it will just run at 6-6-6-18 just like the one he already has.

 

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Yup. All the ram in a computer needs to run at the same frequency and timings and it automatically sets itself to the lowest common denominator.

 

So then, I would be better off getting the set of 2 x 2GB sticks then? Is there a big difference from 5-5-5-15 to 6-6-6-18?

Also, the set I listed above has a "Cas Latency" of 5 while the 2GB single stick has one of 6. Will that make a big difference. Is it also the same 'lowest-common-denominator' type idea?

Here is the single stick one I'd get: http://www.newegg.com/Product/Product.aspx?Item=N82E16820148162

 

Well, thanks for all the help everyone. Newegg had this one which I was originally interested in: http://www.newegg.com/Product/Product.aspx?Item=N82E16820227251

Just saw it on Amazon on sale now for $57 shipped: http://www.amazon.com/OCZ-OCZ2M8004...1?ie=UTF8&s=electronics&qid=1256685695&sr=8-1

Only $17 more than the 1 2gb stick and with better specs, plus I can sell the current 3 gbs I have now. Thanks again for all the help everyone.