Originally posted by: dlxmax
Core2- I'm doing 1600 with a x8 multiplier for 3.2ghz. Something about this system (likely the bios) doesn't like at settings at x6 or x7. I think I was having better success with the x9 multiplier at low FSB's.
akaliel2- vCore at 1.35? I'm sure you could get much more out of just 1.4v!
Is 9 your default multiplier Read this
Here's what I mean...
How we normally calculate CPU Core Clock:
Example: Multiplier of 10x with a FSB of 266MHz yields a CPU core speed of 2.66GHz
Here's how we would now calculate the North Bridge Core Clock (NBCC):
Default Multiplier
/ Multiplier Set X FSB
Example: An Intel E6400 @ 7x500Mhz = 3.5GHz
NBCC = (8/7) * 500 = 571MHz
Since the E6400 has a default multiplier of 8x (8x266 = 2.13GHz) was can see that simply dropping the multiplier to 7x has in effect overclocked the NB!
Note 1: The "Rated FSB" of 4*500 = 2GHz is simply an "marketing effective" way of saying that the Front Side Bus is "quad-pumped" meaning that there are 4 separate 64-bit wide data paths from the CPU to the MCH. Realize that whether you look at it like a single 64-bit pathway running at 2GHz or 4 seperate 64-bit pathways running at 500Mhz it makes no difference in the maximum amount of theoretical data transfer possible per clock cycle.
Note 2: This provided example is dependent on the CPU's default multiplier, therefore an E6600 or E6700, etc. will all scale the NBCC differently...
The NB sets it's internal operating frequency (NBCC) based on the multiplier as set by the BIOS. Rather than set a static value (say, 266MHz) the NB in essence "back calculates" the operating frequency by dividing the CPU core speed by the current set multiplier. Normally, this always yields a stock speed of 266MHz since 266 multiplied by any particular CPU's default multiplier then divided by that same multiplier would always yield the same number....266! Not so when you change the multiplier though!
This helps tremendously to explain why some users reach an "FSB wall" sooner than other and why to this point there seems to have be no explaination as to why someone with an E6400 finds he can reach a higher FSB than someone with an E6600.
Here's what I mean by that:
Case 1:
E6600 @ 7x500 = 3.5GHz
NBCC = (9/7)*500 = 642MHz <- this NBCC may be unachievable by the NB which would artifically create what would be misdiagnosed as an "FSB wall"...
Case 2:
E6400 @ 7x500 = 3.5GHz
NBCC = (8/7)*500 = 571MHz
What we see here is rather interesting....in this case the E6400 CPU may easily reach the outstanding speed of 3.5Ghz, run memory 1:1 @ DDR-1000 AND achieve an amazing NBCC of 571MHz (overclocked from 266Mhz...an eye-popping ~115% increase!) while the user of the E6600 processor, using otherwise identical components, may find that he cannot reach equivalent FSB speeds. The only difference you ask? The default multiplier....
Here's what SANDRA has to say; from what I have seen the only program the happens to report the true NBCC and not just the FSB...
These first two screen shots show how simply changing the multiplier from 8x to 7x overclocks the NB. In this example an increase from (8/8)*400MHz = 400 to (8/7)*400 = 457MHz
Edit: Here is the link to the full article
Article