General OC question/confusion, any input appreciated

[windie]

Hi guys, i have read about OC in the past, and recently also, to increase my knowledge of it. I do understand most I guess, but one thing just keeps confusing me.

Now I know fsb is quad pumped, ram is double pumped, and how you get cpu clock (multiplier x fsb). Firstly, by increasing the fsb, does the ram speed also increase with it? (I know you can fix the rates of other components of the motherboard so the increase in fsb doesnt affect them)

Because, if a person had for eg, ram 800mhz (400x2) and had a motherboard that had a fsb of 1333mhz(333x2), could he increase only fsb to 1600mhz (400x4) to get a fsb,ram ratio of 1:1? OR oc the ram a bit more (400+) and the fsb to get a higher 1:1 ratio? Do you have the option to oc ram and fsb separate?

 

[Mugz]

+5MHz on FSB = +5MHz on RAM. Your FSB is inextricably linked to the RAM, so if you push the one up then the other goes up.

You can OC RAM higher than its rated speed, with a bit of voltage and some heatspreaders.

Advice: improve cooling BEFORE you touch voltage.

 

[windie]

oh i see, thanks for this clarification. Dont have any plans to oc anytime soon, just reading up on it.
So a last thing, to get a 1:1 ratio of fsb and ram, its best then to match it in the start like pc5300 667mhz ram with a fsb of 1333mhz, then whether you overclock or not, its always at the 1:1?

 

[Mugz]

Let's take a real-world scenario:

I'm running a P4 3GHz CPU, mated to 2GB DDR2-800 RAM.

My CPU FSB is 200MHz (quad-pumped to 800), with my ratio at 1:1. My RAM is DDR2-800 (which equates to a 400MHz clock). Since my RAM is running 1:1 with my processor, its speed is 400MHz DDR. If I then set my CPU FSB to 306MHz (where it is now) I end up with a 1224MHz QDR FSB, and my RAM is running at 612MHz DDR. So, yes, matching 667MHz RAM with a 1333MHz CPU gives you a 1:1 ratio.

However, if you use DDR2-800 RAM instead (pc6400 I think) and your ratio is at 1:1, then the RAM steps its speed down to match that of the FSB. This is why you can mix 667MHz and 800MHz RAM in a system and it'll still work. The only way you'll get that 800 RAM to actually RUN at 800 will be to twiddle the ratio (assuming your motherboard allows you to set the ratio) to, say, 4:5.

Most boards will automatically adjust the ratio themselves to maximise the RAM's performance anyway.

Hope this helps.

 

[windie]

Hope this helps.

sure has. Now I believe i get all the concepts behind this and most into overclocking. Will just read up on now how good is having a 1:1 ratio over others like 4:5 ratio you mentioned. Thanks a lot for your posts!