|I tried googling that Shuttle model number & the only thing that came up was this thread? You apparently typed it incorrectly.|
The E6420 is supposed to run at 8 x 266MHz. If the multiplier is lowering to 6x, it's because you have Speedstep (aka EIST) enabled in the BIOS. If you want the CPU to run at full speed at all times, disable it.
And regardless of the fact that you have PC2-6400 which is *supposed* to run at 400MHz, it should be configured to run at 266MHz to match the CPU frequency. Another option would be to increase the CPU frequency to match the RAM...either both at 333MHz or both at 400MHz. That will overclock the CPU though so you'd have to make adjustments to other settings (multiplier, voltage, etc) to keep the system stable. If you had entered the model number correctly, I could have lookeed up the specs & made some recommendations for overclock settings.