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E8400/Asus P5Q OC Guide?

Last response: in Overclocking
July 31, 2008 2:11:14 AM

I recently built my first computer and am now looking to OC it. My system is as follows:

CPU: Intel C2D E8400
MEMORY: G.Skill 2x2GB DDR2-1000 SDRAM
MOBO: Asus P5Q
CPU COOLER: Xigmatek HDT-S1283
PSU: Antec True Power Trio 650W
CASE: Antec P182
GPU: 8800GTS (G92) 512MB
HDD: 2x Samsung SpinPoint P Series 250GB
SOUND: Creative X-Fi Xtreme Music

I've never OC'ed before, but I've read over the "Core 2 Quad and Duo Temperature Guide" and "HOWTO: Overclock C2Q (Quads) and C2D (Duals) - Guide v1.6.1" sticky posts on the forum. I was hoping to find a guide more specific to my particular setup. Does anyone have one in mind or have any individual tips/comments before I begin? Thanks for the help!

More about : e8400 asus p5q guide

July 31, 2008 2:26:13 AM

Know how to clear the cmos and then just start overclocking the FSB. Wait to hit a barrier then increase voltage. Do not send voltage thats way too high.
July 31, 2008 4:30:17 AM

After reading a guide at Legion Hardware, I finally decided to start messing around with my BIOS. I thought 3.6GHz would be a good starting point as the guide cited this overclock to have almost no temperature increase over the stock speed ( However, I seem to be running unsually warm. CoreTemp tells me I'm idling at 51C when my case fans and CPU fan are on high. I started a stress test and had to end it because my CPU speed quickly rose to around 65C. I'm currently using the following settings:

CPU Ratio = 9
FSB Frequency = 400
FSB Strap to North Bridge = 400
DRAM Frequency = Auto

CPU Voltage = 1.25
CPU PLL Voltage = 1.50
FSB Term Voltage = Auto
DRAM Voltage = 2.0
North Bridg Voltage = 1.10

Load Line Calibration = Enabled
CPU Spread Spectrum = Disabled
PCI-E Spread Spectrum = Disabled

CPU Clock Skew = 400
North Bridge Clock Skew = 100

Does anyone have any suggestions where to go next? Thanks!
August 9, 2008 4:07:41 PM

Lets start with the temps. All core temperature readings are derived, it is not an actual reading or measurement. Without getting in to too much detail, the actual sensor reading is the temperature at which the cpu will begin to throttle (slow down) - this is called Tj Max or Tjunction Max. Intel does not publish this temperature. I read some information which would indicate each chip has a slightly different Tj Max (not sure if this is true). In any case, the reading from the Cores are actually the temperature remaining until Tj Max is reached. All software that reports your core temperatures are using this reading to derive your core temperature. As an example, if the Tj Max is 95C and the sensors on a core is reading 55C then the software will report your core temperature as 40C (Tj Max - reading = reported core temp).

The reason for this explanation is there is some debate on the Tj Max for the E8400. Core Temp is using 105C, another program Real Temp uses 95C. So if the program is reading a distance to Tj Max of 45 then Core Temp will report your temperature as 50C (105-55=50), while Real Temp will report the temp as 40C (95-55=40C). What you really need to be concerned with is the Distance to Tjunction Max reading. This is coming directly from the cores and let you know exactly how much room you have left until the chip will start to throttle. I typically do not like to have the distance to Tjunction Max. any lower than 25C but this is not based on any limits, just a personal preference (precaution).

I highly recommend the Temp Guide by Computronix in this forum It provides a much better and thorough explanation on the temperatures

I have a similar rig with the P5Q Deluxe board and a E8400. Idle temps with Core temp are 51C to 53C. There is an option in Core Temp, under the settings, where you can check a box to display the Distance to Tjunction Max directly. In this mode my distance to Tjunction Max is around 54C (remember the higher the better for this number).

OK, with the temps clarified. I can provide a few ideas on the overclocking based on my experiences (note: the information on overclocking is not intended to be a recommendation. Overclocking inherently stresses the componenets and systems and can cause failure. The author of this note is not responsible for any damage, failures, or issues which may occur as a result of overclocking and/or when bios settings are adjusted beyond their default settings).

First, without any changes to your bios, you should make sure your system is stable. I run Orthos for 12 to 16 hours on small fft with a priority of 9. Others prefer Prime 95, your call.

Once you know the system is stable, starting with the default CPU ratio is always good. It helps provide a baseline for comparisons.

Set the FSB strap to north bridge to Auto. If you are interested I can provide additional information for this setting but higher is not necessarily better here.

Change your Dram Frequency to the selection which puts you closest to a 1:1 ratio with the FSB. I personally like setting this rather than letting "Auto" decide. I run 1:1 based on other reports but honestly I have not seen much difference in performance if you prefer to run at a different ratio.

The CPU voltage looks a little low for overclocking however, every chip is a little different. The lower the better but you may have to take this up some to get a stable OC at higher FSB. Running mine at 1.29

Not sure why but had some issues with this board when setting PLL and NB voltages - left mine on Auto.

Looks like you have been doing some reading on the CPU and NB Clock skew. These values look good but to start I would put these on Auto. Again, just to insure a good baseline. These are really for "Fine Tuning" and usually used once you find the max. OC and want to try to push things a little. In other words, if you get an good OC but it lacks stability then these settings may help with the stability.

Good luck and have fun experimenting. Listed below are the settings I am running (16 hours Orthos small fft 9 priority);

CPU Ratio = 8
FSB Frequency = 500
FSB to North Bridge = Auto
DRAM Frequency = 1002

CPU Voltage = 1.29375
CPU PLL = Auto
FSB Term = Auto
DRAM Voltage = 2.1
NB Voltage = Auto

Load Line Cal. = Enabled
CPU Spread Spectrum = Disabled
PCI-E Spread Spectrum = Disabled

CPU Clock Skew = Auto
NB Clock Skew = Auto

Advanced Page
C1E Support = Disabled

Temps as reported by Real Temp
Distance to Tj Max = 52
Core Temps = 43

Distance to Tj Max = 28
Core Temps = 67

Hope this helps