Before we get to any results this is the system I will be using for the initial air cooling results in this thread. Once going sub-zero nothing will change except for the cooling...naturally.
  • MB: EVGA 790i (BIOS P03R2)
  • CPU: Intel C2D E8400 (L746A381)
  • CPU Cooling: Thermalright Ultra-120
  • GPU: HIS HD3870X2
  • NB Cooling: Noctua NC-U6
  • SB Cooling: Thermalright HR-05-SLI
  • PWM Cooling: Swiftech MC-14s
  • PSU: Silverstone Zeus 560W
  • HD: Seagate SATAII 80GB 8MB NCQ
  • OS: Windows XP Pro SP2


Finally, time to show what this bad boy can do...or bad girl I guess. It's just that with such a dark PCB I would hesitate to consider this motherboard to be female. Does anyone know where you can check the sex on this thing? It's not in the manual.

Initial FSB on Air w/E8400
Before we begin, I just want to mention that the highest FSB this particular CPU was able to achieve with the Maximus Extreme or P5K3-Dlx was right around 535MHz for validation and 530MHz for benching on air. That sure isn't the case with the 790i board. We start off with the least stable and will work our way down. That means we begin with the highest CPU-Z validation I could get.

Initial Max FSB on Air w/E8400 - CPU-Z Validation :: 575MHz
click for validation page...

This is a great sign to start off with. I also tried with various lower memory ratios and a lower CPU multi to rule them out but was unable to get anything over 575MHz so it definitely seems to be the wall for this chip on air. With that said, the Maximus Extreme or P5K3-Dlx can't touch this board with 45nm C2D processors for FSB clocking. In reality, there is very little effort involved. Some legwork by Dinos22 got the FSB clocking and then some adjustments from his work got the final push. In the next couple screenshots, I will have voltages as well at the GTL Reference Voltages listed that were used for this suicide screen.


Initial Max FSB on Air w/E8400 - SPi 1M :: 567MHz
click for full size...

Next up is max 1M SPi benchable FSB and as expected based on the CPU-Z validation a solid 567MHz was stable enough to get a couple 1M runs off as well as the screenshot. Again, this is quite impressive and should lead to a single 32M SPi benchable FSB of 555MHz+.


Initial Max FSB on Air w/E8400 - SPi 32M :: 558MHz
click for full size...

As suspected this setup was capable of a single 32M SPi run at just under 560MHz FSB. I was kind of hoping for over 560MHz but I guess 558MHz is close enough. If going sub-zero holds true to history, we could be flirting with 600MHz FSB under the single stage phase or dry ice for 32M but it is going to be tight.


Initial Max FSB on Air w/E8400 - OCCT 12 Hour Stable :: 550MHz
click for full size...

Last but not least is complete stability using a very long run of OCCT on the default infinity setting. As we can see, 550MHz had no problem holding up over the length of the night with OCCT hammering away. I can't say enough about this motherboard and what it is not only capable of as far as FSB goes, but what it un-locked in this CPU that was previously held back heavily by a pair of Asus high end motherboards. Keep in mind, this is still without voltage mods and using the Noctua NC-U6 & Thermalright HR-05-SLI for chipset cooling.

Max FSB after vSPP mod w/E8400 (Single Stage Phase Change) - SPi 32M :: 575MHz @ 1.61v w/Noctua NC-U6
click for full size...

Performing the vSPP mod for higher north bridge voltage has definitely helped increase the legs of this motherboard. The only problem is that the temperature is holding back further gains with more voltage. Anything over 1.61v seems to overload the Noctua NC-U6 but with better cooling, as we will see, the board again inches closer to 600FSB for 32M SPi stability.

Notes About FSB Clocking
  1. nTune sucks but it does help sometimes reach higher FSB clocks...when it works
  2. So far, nothing but nTune allows us to adjust FSB within Windows
  3. In order to reach high FSB I had to POST with higher vCORE than necessary for CPU stability, but then lowering vCORE once in Windows never led to stability issues. nTune is useful for some things, such as voltage control in Windows.
  4. As you might have expected, some memory ratios limit FSB clocks and POSTing ability at higher FSB frequencies...but for the most part, you can use what you want where you want it.
  5. Higher SPP voltage did lead to higher FSB clocks, this should continue to scale with additional cooling on the SPP
  6. This is a big one, setting too much vSPP will result in C3/C1 or double booting errors. That is right...too much vSPP causes this. A vSPP volt mod is about the only way around it as you can then POST with whatever voltage the board will allow, then turn the vSPP up before going to Windows.