memory and overclocking

[zogg]

I have to ask this question. It may sound dumb to some of you but here goes.
Every once in a while I notice that someone will sell some ram or talk about overclocking
and say something like this:

Ram is rated at 150 MHz cas2 but will do 166MHz cas3

wouldn't it be better to stay at 150 Mhz @ cas2 rather then go to cas3 @ 166MHz.
isnt there a signifigant performance difference between cas2 and cas3 ?
Something like 15-20% ?
So if I were to go to cas3 and lose 20% ram performance, why would I do that?
I'm no Mathematician or scientist, but it looks to me that the performance loss of cas2 to cas3 would cancel out any performance increase from the few extra mhz that is gained by adding another clock tick to the memory modules.....I think

 

[Boonesmi]

the 15ish% gain with cas2 over cas3 is only in memory benchmarks, the actual overall system performance gain with cas2 isnt nearly that large (sorry i cant give number, been too long ago i was reading about it) but if memory serves its like 2-5%

 

[MustPost]

Im not sure the exact calcs between Cas2 and Cas3.
But if someones going to OC there processer very high they need High RAM to Match the FSB.
For example Lets say for max CPU OC you needed a FSB of 160. The 150 wouldn't be enought. Possibly u would get better overall preformence by being able to raise the Memory Mhz thus FSB even if u had to lower the RAM to Cas3.

 

[zogg]

I dont know...........ok I see your point

maybe when multipliers get to 20x then even 15 mhz more on the FSB multiplied by a 20x multiplier would equal=300MHz increase in cpu speed. Therfore I could see how going from cas2 to cas3 would help if your goal is getting the most cpu cycles out of your system. I suppose the people on RC cracking teams would want that. But does a gamer want cpu cycles or superior memory performance?


ciao
zogg

 

[Boonesmi]

dont get me wrong, i wasnt saying that cas 3 at 166 was better then cas 2 at 150

only way to know would be to benchmark it. all im saying is that cas 2 doesnt have a total system gain of 15-20% over cas 3

 

[Richardito]

I guess when people do that they are testing the limits of the CPU and sacrifice some memory performance. If you leave the memory @CAS 2 and overclock the FSB the performance increase vs. using CAS 3 is exponential. This means that as you increase the FSB the bigger the gap between CAS 2 and 3 memory performance. I wouldn't sacrifice CAS 2 performance for just a couple of extra MHz on the memory, specially at high FSB overclocks.