Mac Pro RAM configuration question

I just bought a Mac Pro from B&H (delivers today) - 4-core 3.0 ghz/X1900 with one gig of RAM. I want to upgrade the RAM to 8 gig. From Crucial, I note that 8 gigs of 2-gig x4 is $840 vs 8 gigs of 4-gig x2 at $1749.

Looking at RAM from Crucial -- my question..assume that I pull the the two OEM 512's...in getting to 8 gigs there some substantial advantage to using as few DIMMs as possible? IOW, is it worth twice the cost having two of the eight RAM sockets filled for $1749 as opposed to 4 of them filled for $840? Is heat an issue? Timing? Other reasons that fewer DIMMs would be substantially better? Worth the $800+? extra?

And...if I use 2-gig DIMMs x4 (my preference, obviously), I'll still have 4 open sockets in the 2nd riser. Any problem with slapping the OEM two 512 meg DIMMs in that configuration for a total of 9 gig RAM?

robbieduncan said:

The first 4 DIMMS (slots 1&2) on each riser have lower latency that the other 4 DIMMS. This is due to the fact that slots 3&4 are chained off slots 1&2 so requests for slots 3&4 get forwarded by 1&2 resulting in a slightly higher access time.

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Ah. So..better to put 2-gig x 2 in the first two slots of riser 1 and the other 2-gig x 2 in the first two slots of riser 2? Then put the extra OEM 512 x 2 in slots 3 and 4 of riser 1?

robbieduncan said:

Yes.

I'm fairly certain there is a diagram of the order to add RAM etched into the removable side panel of the Mac Pro.

Click to expand...

Yes, there is. I just hooked the thing up, one 30 inch ACD and added the RAM.

Oh my...this is really quite remarkable. I'm in the process of downloading files from my 3 Windows computers on the network. I have to say, that whole Windows experience really look rather pathetic by comparison.