FSB and RAM

K

k1fox

New Member
I have the Intel E7400 processor with FSB of 1066mhz and DDR2 667mhz Ram. Is it best for the ram to run at a 1:1 ratio (ie. 266mhz)?If that's the case then why do ppl buy Ram such as 800mhz and faster for their Core 2 Duo system that have 1066mhz and 1333 Mhz FSB? If the 1:1 setup is best then wouldn't the faster Ram be clocked down to the speed of the FSB?
 
The FSB is quad-pumped, meaning that it will transfer data four times for each clock speed, so to get the actual clock speed you'll divide the rated speed (1066) by 4. Likewise, DDR is dual data rate, so it transfers data twice for each clock tick, so to get the actual clockspeed you'll divide the rated speed (667) by 2.

As you can see, in your case the clockspeeds are matched (it's important to match the real clockspeeds, not the rated/effective speeds).

Oh and to answer your actual question, yes, 1:1 ratio is generally the best; with odd dividers, you only get faster performance if the RAM runs at a speed significantly faster than the FSB.

Sorry for the late reply though.
 
hackapelite said:
The FSB is quad-pumped, meaning that it will transfer data four times for each clock speed, so to get the actual clock speed you'll divide the rated speed (1066) by 4. Likewise, DDR is dual data rate, so it transfers data twice for each clock tick, so to get the actual clockspeed you'll divide the rated speed (667) by 2.

As you can see, in your case the clockspeeds are matched (it's important to match the real clockspeeds, not the rated/effective speeds).

Oh and to answer your actual question, yes, 1:1 ratio is generally the best; with odd dividers, you only get faster performance if the RAM runs at a speed significantly faster than the FSB.

Sorry for the late reply though.
Click to expand...

Can you tell me how this setup looks to you?

E7400 @ 1333Mhz - 333x10.5 for 3.5 Ghz @1.35v :D
2 x 2GB DDR2 800Mhz @1.9v
(fsb:dram = 5:6)

I'm not sure I understood because 1066/4=266 and 667/2=333 so how is that a match?

Can you suggest anything I should change around to achieve 1:1? I have this OC stable right now. thanks
 
if you want to get a better ratio between your fsb and ram spped, then i think you should try to drop your multiplyer down one or two then raise your fsb to 333. if you want your fsb to match your ram speed then you need to have your fsb at 333. is what i did is just put my multiplyer at its lowest, put my fsb to 333, and reboot to see if it will even boot. run y-cruncher, to make sure that ti will go all the way through it. if it does, restart and go into the bios and bump the multiplyer up to the stock speed, or as close to it, boot into windows run y-cruncher again. if all is well then go to bios and begin to raise multiplyer for your core overclock, running y-cruncher everytime until it wont do it. when that happens then down your multiplyer by 1 and you should be okay. you should be able to just set the fsb to 333 with out having to do incriments of 10mhz at a time. just try it i honostly beleive it will be fine
 
Last edited:
vandassen said:
Can you tell me how this setup looks to you?

E7400 @ 1333Mhz - 333x10.5 for 3.5 Ghz @1.35v :D
2 x 2GB DDR2 800Mhz @1.9v
(fsb:dram = 5:6)

I'm not sure I understood because 1066/4=266 and 667/2=333 so how is that a match?

Can you suggest anything I should change around to achieve 1:1? I have this OC stable right now. thanks
Click to expand...
Well they aren't a match - as you said, the FSB:DRAM ratio is 5:6, so the FSB is slower. At 1:1 (the ideal ratio) they would match.

As suggested, dropping the multiplier and upping the FSB would allow you to run the memory and FSB at the same speed.
 
hackapelite said:
with odd dividers, you only get faster performance if the RAM runs at a speed significantly faster than the FSB.
Click to expand...

Just wondering, is this correct: a rig with a cpu running around 300-400 fsb and ddr3 running up at 1600 (800 effective) is gonna be a lot faster (than say, ddr2 800) even though the ratio is not 1:1?

I was curious about this just earlier today... I think I understand it now, good thread.
 
Last edited:
Just wondering, is this correct: a rig with a cpu running around 300-400 fsb and ddr3 running up at 1600 (800 effective) is gonna be a lot faster (than say, ddr2 800) even though the ratio is not 1:1?
Click to expand...
This is correct.
 
so if my fsb is running at 1066 so 266 effectively, and my RAM is running at 800, so 400 effectively, it will make a 2:3 ratio (I'm reading off CPU-Z here)

does this mean I should underclock my ram to make it faster?

EDIT: Would overclocking to have a 300 fsb, therefore generating a 3:4 ratio, be better than my current 2:3 ratio?
 
Last edited:
viper110110 said:
so if my fsb is running at 1066 so 266 effectively, and my RAM is running at 800, so 400 effectively, it will make a 2:3 ratio (I'm reading off CPU-Z here)

does this mean I should underclock my ram to make it faster?

EDIT: Would overclocking to have a 300 fsb, therefore generating a 3:4 ratio, be better than my current 2:3 ratio?
Click to expand...

personally I wouldn't underclock it that much. only small uc's down to 760 from 800 or something, even 740.

I must say I've got my stock 266 up to 380 and 400 so it's easier to get 1:1 with ddr2 800 or 760, irrespectively

you should research oc'ing the e6400!! then you can get the fsb much closer to your desired ratio! if you're gonna oc the cpu it's good to back the ram off a bit so as not to bend it too much till you learn what the cpu can take (this will bring the ram speed down in a bit of a good way). also, make sure you've got the cooling for such an undertaking :)

I don't really know much about what is preferred for ratios, other than 1:1 = good
 
You must log in or register to reply here.
Back
Top