First, you must know that Intel CPU's run on 200Mhz FSB's. Put simply, It is then quad pumped to 800 through the memory and cpu (and that's why the P4's of late
say they run on an 800Mhz clock.
However, that board is based on a 533/400 MHz FSB (that's 133 quad pumped for 533, 200 for the 400). This is important when you try and figure out what 1) CPU speed you are aiming for (multiplier x actual fsb) 2) what the memory can handle. Saying that you are "setting the memory to 400" would tell me that you are aimming way over your head. 300Mhz is HUGE BTW. So, when you say you set it to 400, you're really setting it at 200.
Checking the board's CPU compatibility list
, they don't list the 800Mhz 2.8 CPU being supported, so I'll assume you have the 533 based unit (x21 multiplier). Now, this one goes off of a 133FSB, right? So by setting it to "400" (200) is aiming you at 4.2Ghz! I'm hoping now that you have the 800Mhz chip (x14 multiplier, SHOULD be at 200)
Ok, if none of that makes sense...just get this part:
There's no option for me to keep my ddr speeds at 400.
No, there is none on any board I've seen. It's the FSB setting that you are changing to speed up the CPU. So, the only thing there is that locks the FSB down is YOU. The CPU sets on the front side bus, as does the memory. The Front Side Bus is the highway that connects those two towns together and allows the cars to go back and forth. By upping the speed limit, both rise in speed proportionatly. Why? The speed of the CPU is base on the FSB, and so is the ability of the ram to run at speed. If you up the FSB too much, then you hit that wall that you here about all over this forum (why some buy "faster" memory. Like, PC4200 vs. PC3200).
A CPU's "speed" is base on only two things. The multiplier, and the FSB (as you say you've heard). That mult is locked. Nothing can change that without a doctor's degree in Electrical Engineering and a tool set more awesome than Spicoli's dad's. So we have to run the risk of changing the FSB and speed everything up that sits on it.
This is the very basics of overclocking. I'd do a heck of a lot more research into what you are doing PRIOR to actually doing it. But really look into what you actually have for parts. Again, they made MANY differnt 2.8's that ran on TWO different busses.