I would like to understand ram more....

[icbluscrn]

now that I am not limited by ecs motherboard any longer i can overclock better. I did read the FAQ to get the basics out of the way.

well one question is this> i have the d805 it has 533 fsb with corsair twin2-5400-667mhz. when i check my bios(asus p5wd2-e) at stock cpu frq 2.66ghz it does not show me 667 mhz dram so i cant select,it shows 400 and 533. I have to increase the fsb (dont really remember how much to) then other freq options appear. currently at 187 and i have alot of options up 800mhz i dont know which to pick or what effect will it have? If i pick 800mhz is this like overclocking the ram?

also ram divider< what exactly does it do and if anyone knows where it is on a p5wd2-e

If anyone has usefull links as far as ram that would be nice too

Thanks in advance

 

[The_Prophecy]

the ram divider is the setting that controls the ratio between the RAM frequency, and the FSB frequency. For example, if your FSB:RAM divider was set to 1:1, and the real clock of the FSB (NOT the effective clock) is 200Mhz, that would mean that the ram would also operate at 200Mhz. If you overclock the FSB, then the RAM on that divider would match the FSB frequency. If the divider was changed to.... say 4:5, the FSB clock still at 200mhz, the ram clock would then become 250Mhz. Basically, find what the divider is set to, then find the real FSB speed, divide it by the first number, and multiply by the second number

in the case of 4:5

FSB = 200Mhz, 200/4 = 50, 50 * 5 = 250

RAM frequency becomes 250Mhz.

 

[icbluscrn]

thank this helps a little more. Why would you want to run a divder? is it because you want the ram running higher freq but why? wouldnt you hit the ram limit faster with a divider like 4:5
How is performance effected

 

[Aragorn]

More often you use the divider when your CPU is capable of running with a higher FSB speed than your RAM. In that case you set the divider to 5:4 or 4:3 or whatever you have to so that you can run your CPU to it's maximum potential and then get your RAM as close to it's max as the system will allow.

Sometimes you can get better preformance by scaling back the cpu just a little from its max if it allows you to run your memory at a much better speed. I.E. Your Mobo only allows 1:1 and 3:2 (some older boards did this) your CPU runs stably at 250 MHz FSB but your RAM only works up to 240 MHz. You'll probably get better preformance with 1:1 @ 240 than 3:2 @ 250 (the later would leave your CPU running at the speed it runs at with a 250 MHz bus but the RAM would be almost 30% slower than it is capable of).

In most cases the CPU effects preformance far more than Ram speed so unless you have a drastic case (as above) you are better off maxing the CPU and getting the RAM as high as it can get based on the selection of multipliers you have.

 

[The_Prophecy]

as for your other question, up the fsb speed just enough to make the 667mhz ram frequency available in the bios.... then when ever you want to OC a little more... just increase the FSB speed again...

 

[icbluscrn]

well i cant find anything about ram divider in the bios, but it does let me select the freq. I am at 3.7ghz and the ram freq is something like 770mhz it does let me chose a lower frequency ram if i want it. < so is that the same same thing as divider cause ill be slowing the ram down? or should i run the ram freq at 667 to the highest the fsb run stable then raise/lower the ram freq?

Oh by the way thanks everyone for your help

 

[The_Prophecy]

well i cant find anything about ram divider in the bios, but it does let me select the freq. I am at 3.7ghz and the ram freq is something like 770mhz it does let me chose a lower frequency ram if i want it. < so is that the same same thing as divider cause ill be slowing the ram down? or should i run the ram freq at 667 to the highest the fsb run stable then raise/lower the ram freq?

Oh by the way thanks everyone for your help

Set the ram frequency at 667, then adjust the FSB frequency as you see fit. The divider is adjusted for you when you set the ram frequency in the bios.

 

[Aragorn]

To elaborate a little on what prophecy said, the bios is udjusting it's ram divider in the back ground to make whatever frequency you selected work.

That is in some ways better and in some worse than adjusting a ram divider and being stuck with whatever ram speed you get when you find your processors max. It can create really strange multipliers that will not be good for preformance and the only way to know would be to have the knowledge to back track from your 2 frequencies to figure what divider it will use and then to know wheather that is a bad number or not.

I suggest you do as suggested before and leave your RAM set to 667 and then max our your processor. Once you find the highest speed at which your processor will run stabily back it off about 5% to help guarantee it will stay stable even if your room gets warmer or whatever. Then slowly up your RAM speed and figure out what gives you the best preformance. Either use benchmarks or subjective methods (actually gaming or crunching data).