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My Operating Systems class Instructor at College claimed that with DDR SDRAM, the more you have of it, specifically, if you have more than 2 sticks of DDR SDRAM, it will actually make your machine run more slowly, and the more you add, the slower it will run because of how the RAM sync's with the CPU and system bus. Is this true or a load of BS?
 

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hmmm, this is news to me, it seems unreasonable.
Maybe in some systems with buses that dont play nicely with the ddr ram.
You are definately better off with more ram on less chips ie: 512 MB on 2 chips instead of 4.
 

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I have my doubts about it.

Each system, each architecture, each configuration is different when it comes how well performance is optimized and exactly what the bottleneck is (by definiton, there has to be a bottleneck).

There are just way too many variables to say such a thing.

There is also the problem of looking at a system, ie a hardware/software combination, and treating it as if the software didn't exist or has no effect on performance.

More memory can increase the time certain tasks take, there's no doubt about it. Startup on a Mac, for example, involves a memory test. It's obvious that startup must take some small amount of time longer if more memory is installed. But using the computer is much faster with something above 100% of the optimal memory for a given task.

I don't see the point of his comment.
 

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I think the more I play DDR, the faster I get. I also today just happened to... Oh wrong DDR.

I've never heard anything like that, and my guess is that your instructor might have experienced it with a particular system where the bottle neck was RAM, or something similar to the PCI card system in the new G5s. In that if you put in a slower card, it slows the whole bus down, and somehow on that system the bus slows down to accommodate more RAM.
 

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Is it possible that your instructor is getting DDR RAM mixed up with dual channel RAM. Having done a bit of research on this very topic last night: Dual channel RAM motherboards require RAM to be installed symetrically e.g. two 512s or 1024s etc. Standard RAM configurations (using DDR) as seen in todays PowerBooks for example, can use any combination of RAM (according to Kingston Technology - www.kingston.com) to reach their maximum.

It's funny b/c I had heard the same thing about DDR, but I suspect perhaps that people are confusing DDR with dual channel...

I'm planning to increase my PB's RAM to 1024 and will install an additional 512 stick.
 

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If the DDR is dual channel, it can actually be more efficient to install chips in pairs (IE, if you want to add 512, put in 2x256), otherwise it shouldn't make a difference.

For most purposes, the more RAM you have the better.

--PB
 
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