Question on RAM and FB-DIMMs

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Hi all,

I just recently bought myself a Mac Pro. I have a relatively stupid question that I'm hoping I can get some quick assistance on: I bought the cheapest memory option (2 gb) since I found the price of adding RAM from the Apple website to be prohibitively expensive. Now, from what I understand, and please do correct me if I'm totally wrong, the RAM needs to be added in pairs and in order to fully take advantage of the FB-DIMM configuration is to have at least 4 sticks installed. My question is, if I want to bring the total RAM of my system up to 4 gb, will I be able to just get 2 more 1 gb sticks, or do all 4 sticks have to be matched somehow? Also, if I wanted, say, 6 gb instead, would it matter if I had 2x1gb and 2x2gb?

Finally, I'm considering either crucial or OWC RAM. I'm assuming that unless I do have to match all 4 sticks, I'll be okay "mixing" apple RAM and other brand RAM, but please let me know if I'm wrong on that as well.

Thanks!
 
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As far as brands, you should be ok mix and matching as long as the speeds are the same. I had a guy do it the other day with some Apple and some Mushkin. Other than ordering the wrong speed (5300 when he needed 6400) the first time, it worked just fine. However, make sure that each pair of slots are identical.

http://manuals.info.apple.com/en/MacPro_MemoryDIMM_DIY.pdf

That has an image showing which slots are which. Just make sure your speeds are correct, and that each pair is identical size/brand.
 
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As far as brands, you should be ok mix and matching as long as the speeds are the same. I had a guy do it the other day with some Apple and some Mushkin. Other than ordering the wrong speed (5300 when he needed 6400) the first time, it worked just fine. However, make sure that each pair of slots are identical.

http://manuals.info.apple.com/en/MacPro_MemoryDIMM_DIY.pdf

That has an image showing which slots are which. Just make sure your speeds are correct, and that each pair is identical size/brand.

Another question I can't find the answer to is what is the difference between pc 6400 ram and mac 6400 ram. I don't know.
 
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With only 8 slots, and if all DIMMs must be equal size in pairs, total GBs of Ram can only be 2,4,6, 8 or 4,8,12,16 or 8,16,24,32 ??

My friend just told me he got 10GB of RAM which means he must be a little redundant somewhere?
 
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also - will 1 pair of 4GB memory (8GB) give better performance than 2 pairs of 2 GB?
 
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The pairs have to match, that's about it. You can toss in 2-2GB and 2-1GB and 2-512MB and be ok. I believe it works or works best if you install from the higher capacity to lowest.
Apple doesn't make their own brand RAM; it's most likely made by Hynix. Yea, hadn't heard of them before Apple started using them. You can mix brands no problem.
Last question, it believed that 4 modules will give you better performance than 2. I asked someone more knowledgeable than me about this topic and he said that this might only be the case with Mac Pros with 2 processors. Something to do with the way the data is going back and forth between the RAM and processor(s). I don't know if any of this is true or what the performance gain is but if it's true, it can't be very noticeable. The Mac Pro's crutch certainly isn't the processor or the RAM.
I have never heard of mac 6400 ram. RAM is not specific to Macs or PC.
 
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I would think it's the HD. Faster data rates would certainly be nice.
 

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