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Q9400 400fsb concerns

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April 13, 2010 1:39:47 PM

Ok, So my new found overclocking hobby is bringing me some concerns. Im still prime95 testing my OC's but I would really appreciate some extra input on my current situation.

Ive recently decided to try pushing a bit past the easily reachable 3.0 OC on my q9400 and asus p5q pro.

My current settings are as follows:

Hardware- P5Q Pro Mobo / C2Q Q9400 @ 3.2 / Gskill ddr2 1066 5-6-6-18

CPU multiplier is 8x
FSB strap to north bridge 400fsb
cpu frequency 400 X 8 = 3.2ghz

"LLC and spread spectrums disabled"
"AI Clock twister = Light

Ok so for my questions. As i have been testing different overclocks, I have noticed that as you change cpu frequency often your ram frequencies also automatically overclock as well.
I recently went for the 3.2 OC and everything has booted up no problems. "cpu voltage 1.25"

I changed the cpu frequency to 400mhx X 8 to get my desired 3.2 speed. I also set the fsb strap to north bridge to 400fsb as well as it seemed this would be the best match for frequencies. After doing this my ram frequency options offer me the correct ddr2 1066 option that i did not have @ 3.0 "closest option was ddr2 11xx when at 375 x 8.

After successfully booting the 3.2 OC I took a look in asus's AI Suite and noticed the fsb is reading 1599.88 and the little meter is in the red nearly maxed out now.

My big question is are these frequencies with 3.2 stable with fsb strap to NB @ 400 and FSB showing as 1599.88 in ai suite.


I use my system mainly for gaming But I dont want to risk damaging it .


Any help greatly appreciated.

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April 13, 2010 2:59:27 PM

ny_nick said:

My big question is are these frequencies with 3.2 stable with fsb strap to NB @ 400 and FSB showing as 1599.88 in ai suite.

As long as your temps are below 70 C and your vcore is at or below 1.3625 volts, you are good.

You are confusing FSB frequency with the FSB clock.

Definition time (attention purists, I'm talking about DDR2 and I'm simplifying a little :) ):
Core2 CPU's use a frontside bus (FSB). The FSB is a thing with two main characteristics: speed which is usually defined in MHz and width which in the Core2's is 64 bits wide. We are concerned with the speed.

Using the Q6600 as an example, the FSB frequency is 266 MHz. The matching DDR2 memory clock for that frequency is 533 MHz (266 X 2). DDR2 memory transfers two chunks of data for each bus cycle, hence double the frequency. So, to run 1:1 at an FSB of 266 MHz, we need DDR2-533 RAM. What CPUZ does is a little confusing. It will tell you that the memory frequency is 266 MHz for a 1:1 ratio.

The FSB clock is 1066 MHz (266 X 4). The bus is "quad pumped". It transfers 4 chunks of data into and out of the CPU each cycle. So each FSB cycle generates 4 FSB clocks.

Now, if you increase the FSB frequency to 400 MHz, the corresponding memory clock is 800 MHz and the FSB clock is 1600 MHz.

I always run my memory at 1:1. That is the FSB freq to mem freq ratio of one to one. That means that the memclock is twice the FSB freq. Running memory slower costs performance. Running memory faster does not give you much if any real world performance increase and it can lead to higher instability.
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April 13, 2010 3:07:58 PM

Thanks for the reply that was just what i was looking for. But i have my memory set to 1066 not 800 Oops. But* everything is stable it seems to appear now.

cpu temp almost never above 30 degrees under gaming load.

MB tem rarely but sometimes spikes to 40-45 max.

I will try the ram set to 800 thx
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