XPS 9100 RAM upgrade options

If you're asking if you MUST run in dual or triple channel, with all matching modules in each channel, the answer is no.   It only depends on how the modules are allocated - in a 6-slot system, each set of 3 (pink vs blue) can run in single, dual, or triple.  If you have 2x2GB in 1 and 2, and 2x2GB in 4 and 5, then you're in dual channel.     Reliability is not an issue - the memory controller can handle any mode.

<ADMIN NOTE: Broken link has been removed from this post by Dell>

As for faster:  Capacity is always way more important than speed.   But if you've got enough capacity,  interesting benchmark below on the average performance difference when allocating it with single/dual/triple channel - it's a measurable advantage, but not by much.    If you're a serious hard-core performance enthusiast,  maybe it's worth doing whatever it takes.   But to me as an average user,  that extra 4GB module is maybe $50 for a theoretical 3%, plus you have the indirect cost of throwing away $40-50 worth of perfectly good memory.    Just not my style.

http://www.tomshardware.com/reviews/Intel-Core-i7-Nehalem,2057-13.html

What I don't know is if  2 dual channels is better or worse than 1 triple plus one single,  - e.g, you juggle the modules around so the 3 2GB are in triple, then throw the extra 2GB plus the 2x4GB into the second set of slots.

Just in case:  Unless you run programs that genuinely require that much memory, like CAD/Video/3D graphics, or maybe a seriously heavy-duty game,  adding more won't do anything for you.   The idle capacity will just sit there twiddling its transistors.

I may test whether there is any speed difference between single, dual or triple.

What would be a simple way to test?  Just time some ZIPing or rendering? (I'm using the computer to run Aodbe Premiere and After Effects.)

Well, I really messed up my first reply.   :emotion-10:    Forget what I said about combining triple/dual in different banks - your whole system will only run in one mode.   To be certain everything works the way you want, you may still end up wasting something....

You have 2 banks - blue and pink.   Each bank has 3 channels.  Dual or triple means combining the channels within each bank.   To get dual, you have to have identical pairs of modules in either one bank, or both banks.  To get triple, it has to be identical sets of 3 modules.

In your current configuration, you're in dual channel - 2x2GB in Pink, 2x2GB in Blue (the BIOS should say so under Memory).  2x4GB in Pink and 2x2GB in Blue (or vice versa) should also function in dual channel. 

To get triple channel, all three modules in each bank have to be identical:  Pink1=Pink2=Pink3, and/or Blue1=Blue2=Blue3.   3x2GB in Pink,  3x4GB in Blue, for example.

If you did, say, 3x2G in Pink, then 2x4GB in Blue, the whole system would at best run only dual channel, but likely only single.   Since Dell uses custom motherboards, and they're not publicly documented, the only way to know for sure would be to install it, then go into the BIOS and see which mode it's running in.   Even the commercial motherboard manuals I found aren't that specific about it, either. 

Here's where I really need to apologize.  Mixing up different sized modules within one bank might work fine, but it might not - PC's can be very fussy about it..  If you do mix in, say, 2x4GB with 1x2GB in the same color bank,  if the PC is unhappy it either it won't boot or it'll throw an error.     That's why most vendors sell modules in sets of 2 or 3 - that way you're reasonably sure the pair or triplet will play well together.      If it does work, then everything will probably revert to single channel.    

So that leaves you with a dilemma, and the 16GB limit doesn't help.  To max it out and be done with it, even if it is wasteful, buy 3x4GB modules for one bank, then put 3x2GB in the other.  Or, be frugal and experiment with 2x4GB, but be prepared to be limited to only 14GB total,  or at best 16GB in single channel.   In any case, be sure the vendor has a generous return policy.   Crucial is pretty good.

But the rule still holds - capacity is more important than speed or bandwidth.  Having 12 GB in dual or triple channel will not compensate if you really need 16 GB.

As for testing it out - someone did it with 3DSMax, though that was dual, not triple, and they throttled the memory usage to test it out (see last post in thread below).    I assume you could do something similar with Adobe.  Afraid I'm not a performance guru myself.

http://en.community.dell.com/support-forums/desktop/f/3514/p/19337001/19714264.aspx

Came across this from Adobe, which may help:

http://help.adobe.com/en_US/aftereffects/cs/using/WS9F936D13-E76A-41e4-BF8F-577132AB4723a.html

just run the http://www.crucial.com/ upgrade tool.