What is the diffrence in ram type?

[tjr2mental]

I am getting a XP 2100, Epox 8rda (not the plus as I did not see a diffrence that would matter to me... they overclok the same right?) and need some ram to finish it all off. Going to crucial's site I go to the section where they list the ram that will work with the board that i selected. Now my thing is what is the diffrence between these two chips?
DDR PC2700 ? CL=2.5 ? Unbuffered ? Non-parity ? 6ns ? 2.5V ? 64Meg x 64 (118.99)
DDR PC2100 ? CL=2.5 ? Unbuffered ? Non-parity ? 7.5ns ? 2.5V ? 64Meg x 64 (99.99)

What is the 6ns and 7.5 ns? Will I see a diffrence in the ram if I over clock the processor that I am getting any how. Is one better then the other? Also, seeing as how all the ram that I have is crucial (pc133) and have not had any problem with it at all wouldit be best to stick with them when I go to ddr. When I got my pc133 chips people here said that they were the best. Is this still true?

 

[Amber]

The PC2700 is 333mhz
and PC2100 is 266mhz

so the PC2700 is faster,
it's like PC 133 and PC 100

 

[Jeff7]

The techie in me refuses to be restrained.
Technically, it's 133MHz and 166MHz, it transfers data at both the rising and falling of each clock tick. The effective speeds are 266 and 333. And it'd be more like PC133 and PC166 (though I don't think there actually is an official PC166 standard).
Ok, the techie is now happy, and will go sit in his corner again.
If you want to overclock the bus, the memory's default speed will of course help determine your overclock speed. Get PC2100 (133MHz bus), and you might get up to 150; use PC2700 (166MHz bus) and you might get to 175 - those are just examples, I did no research or calculations there. But if you're getting an XP2100, it'd be best to give it the PC2700 - that helps the processor have a quicker supply of data to process.
From what I've seen, Crucial is still very popular around here.

 

[Zepper]

"From what I've seen, Crucial..."
Jeff7, are we to get the impression from the above that Crucial memory is non grata at your house?
.bh.


p.s. Oh yeah, my techie wants out too. 6.0 or 7.5 ns (nanoseconds) is the guaranteed minimum time that the modules can respond to a memory request, and that is usually a conservative rating. You can determine the equivalent MHz by dividing the nanoseconds into 1 and shifting the decimal. e.g. 1/7.5=0.1333, shift the decimal 3 places to the right et voila 133.3 MHz; 1/6.0=0.1666, shift, 166.6 MHz. And since it is DDR memory the module responds with two lines of data effectively doubling the rate.bh.