RAM speeds with current bus speeds

[wishfool]

I have a question that has probably been answered buried deep in some topic but here it goes.

*disclaimer: I'm new to all this and all this is based on research and not actual experience.

There's CPU's with 1333MHz FSB which is 333MHz CPU frequency. Don't think I've seen overclocks past 500MHz without extreme cooling which would translate to ddr1000 (am I right here?). Is it beneficial to run out of 1:1(CPU frequency:RAM frequency) ratio? What are the benefits to running at 1:1 ratio? I've heard that it's good to run at 1:1 but wonder if that's the antic of yore and if it's just as good to run at 1:2 or so.

 

[cprince]

I think that you got the CPU frequency and FSB frequency mix up. 1333MHz and 333MHz are all FSB frequency. On Intel platform, the FSB is "quad pumped," which means that there are four data transfers per clock. The 333MHz is the base frequency, and the 1333MHz is the "quad pumped" frequency(4 x 333 = 1333MHz). CPU speed is the base FSB frequency times the CPU multiplier. For instance, a Core 2 E6550 has a multiplier of 7x, so 7x333 = 2.33GHz. The RAM speed is also derived from the base FSB. There are a few multiplier settings that the BIOS has for RAM. For Core 2 processors, it is best that the RAM multiplier be an integer multiple of the FSB, i.e. 1:1, 1:2, etc... instead of the weird multiple like 3/2, 5/6, etc... However, the performance different is so small that it is negligible.

 

[sutahz]

He did use "cpu freq" incorrectly, but we all understand using context clues. Your very on track. 333x2=DDR667, 533x2=1066DDR. Running your ram in sync w/ the fsb is beneficial because it reduces the latency in accessing the ram. You have to overclock your ram 50% over the FSB to have the increased speed overcome the effects of being out of sync. For example, its better to run ram at 533MHz then at 667 (w/ a 1066FSB cpu) but running it at 800 gives slightly better performance then 533. 800/533=1.5 (150% of 533). Given that, thats results using synthetic benchmarks, not real world. When we step into the real world of windows, games, adobe, etc, what speed your ram is running at, AND its timings (ie DDR800 @ CL3 v CL5) is negligable. If your running a folding@home or SETI or such, perhaps those would benefit from tweaking the RAM... I'm not for sure.