I am having a discussion with a co-worker who is all about #'s on a computer. This discussion was on the speed of memory and the effects on a computer. We were looking at a Dell computer Dimension 2400 P4 2.8 Ghz w/ a FSB of 533, 512 MB Dual Channel DDR SDRAM at 333 Mhz (166 each channel I am assuming). He stated that he would not purchase RAM with a speed less than 400 MHz.


I guess my question is:

To the AVERAGE user watching DVD’s, Burning CD’s, surfing the Internet, and writing letters, would there be a noticeable difference in their computer with a memory speed of 333 Mhz vs.400 Mhz?

it would be negligable at best.

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jlanka (. .)
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Unless you can find 333 mhz for cheaper than 400 mhz, theres really not much of a reason to go with it, why not just buy the 400 mhz ram in case you might use it in a future upgrade

Well, OK, here's the deal.

The RAM you're refering to is Double Data Rate, that means 166MHz clock rate has a 333MHz data rate. The CPU you refered to is Quad Data Rate, 133MHz clock rate has 533MHz data rate. Dual Channel allows the RAM to have twice as much bandwith as single channel, to match the CPU.

Given that information, PC2100 (DDR266) Dual Channel would be fine for a 533 bus CPU. I don't know why they are using PC2700 (DDR333) unless it just happens to be cheaper at the moment.

Either way, DDR400 doesn't come into play until you have an 800 bus P4. The 800 bus is a perfect match for DDR400 Dual Channel. The added bandwidth of DDR400 would be unused by the slower 533 bus speed.

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Thanks everyone for your help and explanations. It really is appreciated.

Got a slightly different question related to the same topic.
I have a 2.6 GHz machine 800 FSB which has 4 slots and came with 2 PC2700 512 that run at 333. I bought 2 OCZ 1GB low latency PC3200 sticks that run at 400. However if I add the 2 512s in they all run at 333.
Does that force the FSB down to 667?
Is it better to run XP pro with 3 GB running at 333 OR 2 GB running at 400 (an even multiple of the FSB)?
Thanks,
Mike

I should add - that I am sure the PC2700s have a higher latency. How do different memory latencies affect performance?
Mike

If you put fast ram in with slow ram, the fast ram downclocks itself to match the slow ram. As for timings, I'm pretty sure they also slow to the lower set.

OK, I understand that but to my specific questions:
Does that force the FSB down to 667?
Is it better to run XP pro with 3 GB running at 333 OR 2 GB running at 400 (an even multiple of the FSB)?