800mhz DDR = 400mhz x2 for Double Data Rate effective.
However, you may have to disable the auto feature to change the timings.
If you do, be sure to keep it set to 400mhz.
You can lower the timings manually to what they are supposed to be.
I have heard that Patriot Memory does this, the auto setting will keep the timings at 5-5-5-12, you have to lower them to 4-4-4-12 manually.