DDR3 RAM speeds and overclocking

Hi

I've been planning to buy a new DDR3 system later this year, and most things are sorted, but I had no clue whatsoever about how the ram speeds and so on worked. Looked up a load of websites, and eventually got together some kind of idea about how it all worked, but I could really do with someone checking it over and letting me know if I've got anything right or not. I posted up on a couple of other forums, but nobody responded... so either they hate me or I bored them so much they gave up before the end of my post

I was hoping someone here might be able to help

I'm probably looking at a Gigabyte P35T DQ6 and an e6750. So with that processor, it runs at a stock bus speed of 333mhz quad pumped to 1333mhz, but it looks like it's possible to achieve a bus speed of around 500mhz (again, just for the sake of my maths)

In that case, a FSB : DRAM ratio of 1:1 would give me ram at a frequency of 500mhz, and as such DDR3 1066 should work perfectly well, being that 500*2 is 1000. Or alternatively I could set an FSB : DRAM ratio of 5:8, getting me ram at a frequency of 800mhz, and use DDR3 1600 instead.

Presumably in the 5:8 alternative, I'm sacrificing tight timings for a higher clock speed. But at the same time, I've heard that 1:1 is the ideal ratio for C2D processors. So what I'm trying to discover is firstly, whether my maths actually makes any sense, as I didn't understand any of this ram speed business a little while back, and secondly which option makes more sense.

Any help would be really appreciated

Give this a shot: http://www.tomshardware.com/2007/08/30/the_new_arms_race_ddr3-1800_ram/

Yeah, that article is what inspired me to actually try and work all the speed stuff out for myself, rather than just waiting til I buy and asking on the forums for someone to suggest some RAM to go in the system

I guess it might just be best to go for DDR3 1600 or 1800 chips and see what I can manage with it

To achieve max theoretical bandwidth you need a 1:2 divider, because FSB is quadpumped and DDR is "only" dual data rate. So, at equal frequencies FSB is twice as efficient, and the width is the same (FSB is 128bit, DDR is 64bit times two [dual channel DDR]).

To make it simple, just disregard the real frequencies and look at the effective/rated speed only, FSB 1333 and dual channel DDR1333 has the same theoretical bandwidth, but the real frequencies are 333 vs 667, therefor 1:2 is optimal (but small real world difference from 1:1). Too see the difference for yourself you can use the built in benchmark in WinRAR, it loves high memory speed.

Thanks a lot for the info, makes a lot more sense now

Are there any diagnostic utils out there display your current memory speed and/or the divider (outside of BIOS)?

Duh, ignore me - just noticed everything is on the memory tab of CPU-Z.

LOL i have the E6750 it has been running nice, i have junk value ran and it in my opinion (along with the MB really ) it is the only thing holding it back, i have it at 1600 (400FSB with 8x multi = 3.2Ghz and my memory at 800MHz (400*).

With DDR3 Ram and nice MB you will be able to get great results