What is faster 2 2GB sticks of RAM or 4 1GB sticks of RAM?

4 slots of available memory, considering upgrading to more.  have 4GB max. Windows XP.  May only upgrade to 2 x1GB sticks.  Just wondering what you all think?
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Lee W, MVPTechnology and Business Process AdvisorCommented:
There should be no significant measurable difference.
Gary CaseRetiredCommented:
It's better to use 2 2GB modules -- not for any appreciable speed difference (although there may be a small advantage -- more in a bit) -- but for a more reliable memory subsystem.

Most desktop systems use unbuffered RAM modules -- this results in very large loads on the address and data buses when you have more than 2 modules installed, and can significantly degrade the signalling on these buses.   The memory subsystem "sees' one load per memory chip -- so with 2 modules installed, that's up to 32 loads (with double-sided modules) ... and with 4 modules installed that's as many as 64 electrical loads on the bus.   Some systems automatically adjust for this higher load by either increasing the voltage a small amount; reducing the clock frequency of the memory (thus slightly slowing it down); or by adding a cycle to the SPD's latency setting (again, slightly slowing it down).   These adjustments help keep the memory subsystem reliable -- but mean that 4 x 1GB modules would be slightly slower than 2 x 2GB modules on these systems.   But regardless of whether there's any timing differences, the memory will definitely be more reliable with only 2 modules.

For a bit more detail on this, watch Item 10 on this presentation:  http://www.corsairmemory.com/memory_basics/index.html

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