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AMD 790FX 4-Way Motherboard Roundup

By Zachary Chan - 10 Mar 2008

More Overclocking

Advanced CPU Multiplier Controls

For hardcore overclockers, some motherboards even offer advanced features for custom P-State control, enabling fraction multiplier values for CPU and NB multipliers and voltage limit control, an essential feature for serious overclocking endeavors with a Phenom. The DFI LANParty DK 790FX-M2RS was the only board to come with some advanced P-State control to allow CPU and NB frequency tweaking, but still no P-State voltage settings.

CPU sub-menu with advanced options to tweak CPU and integrated NB multipliers.

The formula to derive the actual multiplier fractions using these advanced controls are calculated as below:

  • CPU Multiplier = (CpuFID+16)/CpuDID
  • NB Multiplier = (NbFID+4)/NbDID

Here's an example of a fractional and extreme number that can be achieved using the CpuFID and CpuDID controls to tweak CPU multiplier. Notice that our CPU multiplier is 2.47x. No, that's not a glitch and it really works.

2.47x CPU multiplier - You will never be able to get fraction numbers, or even a multiplier this low through the BIOS.

AMD OverDrive

AMD's OverDrive is an exceptionally thorough system monitoring and overclocking tool for tweaking the Phenom processor. You have access to just about all entire host of Memory timing parameters and even manually control individual CPU core multipliers on the Phenom, a feature that we've yet to see available on any BIOS-level overclocking. However, OverDrive seems to be very restrictive when it comes to motherboard and HT overclocking. We've dramatically failed to perform HTT overclocking using OverDrive on all four motherboards we have at hand. At most we've been able to push it up by 10MHz, but in most cases, Windows freezes up even at such small increments. Also, there are no NB and Memory frequency controls accessible from OverDrive, which breaks the various dependencies for HTT overclocking. Do take note however, that the OverDrive tool itself is still in a beta stage at the moment. The functionalities it offers are already comprehensive enough, but stability is something AMD should be focusing on now to make the tool more useful for overclocking.

CPU overclocking controls. Great for setting individual core performance, not so great for HTT overclocking.

More memory tweaking functions than any BIOS provides. But, you can't change memory clocks on-the-fly.

Basically, you will still need a good motherboard with an overclocking BIOS for AM2+ overclocking. OverDrive is a supplemental tool offering finer control of each of the Phenom's core, but otherwise, it's just another monitoring tool at present.


Overclocking Testing

For this test, motherboard overclocking was performed the traditional way of reducing the CPU and Memory frequencies to safe levels in order to see how far we could push the HTT frequencies alone. HT Bus multiplier was also scaled down to effectively reach higher base clocks. As expected of the MSI K9A2 Platinum was the lowest performer because of a lack of NB multiplier, which kept the HT Bus frequency too high. The ASUS maxed out at 270MHz, while both Gigabyte and DFI topped at 275MHz. Regardless of how low we set the HT Bus multiplier, it would seem that 270MHz is the average maximum that the chipset can handle.

Considering the complex relationships for AM2+ overclocking and our results, it would seem that there is really limited value in pursuing ultra-high HTT frequencies when overclocking an AM2+ motherboard.

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