FSB, RAM & Multiplier

ericmlaing

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Dec 4, 2008
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So I'm wondering... I have an E7400 (10.5x) - My FSB is at 400 as I want my RAM at a 1:1; test after test with p95 and the like and have successfully clocked to 3.8 without having an issue. Adjusted Vcores (Bios) to good levels (think my highest ever was 1.26). Ya... only issue I ever had was I chickened out going to a 400x10 because I didn't have the time to watch p95 and see what the temps would be. All temps were okay at 3.8.
So, my P5Q-E MB is alright, I'm happy with it... the E7400 is a 10.5 like I said, so I could bring the chip to a 400x10.5 clock max... or is it max?
What happens if I bring the FSB higher (can go way up actually) and the multiplier etc etc... let's say, hypothetically, I got the chip (not like I ever would - not on air cooling or for what I use it for) up to 5.8GHz - what happens to the RAM? If the FSB @ 400 gives a 1:1 wouldn't say, a FSB @ 800 be a .5:1 and hence, reduce my RAM efficiency? Is that when you want higher RAM (1066 or whatever instead of 800?).
Just curious. My math is sucking today.
I have spreadsheet after spreadsheet of my OC's, temps, speeds, voltages etc just to see what works best. Sandra has been helpful ful the Mops and all and the spreadsheets let me see 'bang for buck' kind of thing. As is, 400FSB, RAM 1:1, Vcore (in auto of all things), x of 9 (so 3.6GHz) gives the best performace/temp ratio of all.
 

festerovic

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The RAM speed listed in the settings is just a ratio. So if the FSB is 400 and the ram speed you pick is 800mhz, then you run 1:1, like you said. With that same setting, if you raised the FSB to 800, the RAM would run at 800mhz, which is double the speed of ddr2800. And yes, if they had ddr21600, that would be the way to go.

As to efficiency, I have heard lots of people say that 1:1 ratio is best for performance. In many benchmarks, the running speed of the ram will probably show a bigger performance gain, so lets say you had FSB of 333, and you had ddr2800. You wouldn't run a 1:1, but since the RAM is running faster, you might get more performance (on benchmarks) than if you had run it at 666mhz (1:1 for that FSB)