mixing different size memory Dimms

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Hi Guys;

Can someone tell me how much of a disadvantage there is to mixing
different size memory Dimms.  Specifically, I'm looking at purchasing a

del XPS M1710 laptop which can support up to 4gig of RAM.  Ideally I
would like more than 2Gig of ram but can't afford Dell's 4gig
configuration and they don't offer a 3gig configuration.

So, I was considering getting a 1gig DIMM and a 2Gig Dimm from a third
party vendor
http://www.4allmemory.com/search/dell/xps.cfm?q=Dell+XPS+M1710 .

My understanding is that if you mix the Dimm sizes, then you lose some
performance because the dual channel can't be used - or something like
that I don't quite understand.

So, am I still better off performance wise with 3gig as opposed to 2gig

(meaning 2- 1gig Dimms which obviously match in size)

Thanks for your help!

Re: mixing different size memory Dimms

joet11@comcast.net wrote:

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For gaming purposes 2x1GB will be plenty. The advantage of identical
quantities of RAM on each channel, is the Northbridge fetches data
128 bits at a time, instead of 64 bits at a time. That is dual channel
operation, and in the past that could give 30% more memory bandwidth.
But the application level improvement will be a lot less than that.
In the best case (a program purely dependent on RAM), you might get
a 10% improvement in application execution time. Your processor has
a pretty good sized cache, so the impact in most situations will be
less than that.

For Windows applications, I cannot think of too many usage scenarios
where the 3GB will be visibly superior to 2GB. If you were a Photoshop
user, the images you'd be working on would have to be pretty big to
justify the larger memory. If you were an engineer doing circuit design,
maybe some simulation application could use the memory. But for
everyday Windows use, 2GB can allow keeping a ton of applications
open at the same time. I've only heard people claim one game as needing
more than 1GB, so 2GB should handle anything you want to do.


Re: mixing different size memory Dimms


Thanks very much for the explanation.  I really appreciate it!

Paul wrote:
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Re: mixing different size memory Dimms

On 17 Aug 2006 09:20:58 -0700, joet11@comcast.net wrote:

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Dell charges a pretty penny for memory.  You might consider
buying the base (least amount possible) config then buying
3rd party memory.  If the system's base config is 1GB or
less this will likely be cheaper.

You do want a pair of matched modules for dual channel mode.
They need not be a "kit" per se, buying two single models at
same time is usually sufficient, odds are quite high you end
up getting two identical modules this way but of course it
is not guaranteed, memory manufacturers change things every
once in a while.

With same density memory, having too much will use more
battery power.  Not a "lot" relative to other things, but
unless you have need for 4GB, might as well stick with 2GB.

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