Odd RAM and CPU issue...

I've recently bought some Corsair 6400 ram (1 gig per stick) and I've noticed an odd occurrence. I plug them in to my current computer and the CPU drops from 2.2ghz to 991mhz. I plug in the old RAM and it goes back up to 2.2. It's an AMD dual core 4200, dunno if that has known compatibility issues or if my CPU is truly just running at half speed. Ever since I bought the computer I've noticed that it is often slower than my 1.8ghz computer, so I'm partial to my CPU running on one core. Anyone have any similar issues and know how to fix it?

If you are seeing 667 on the post screen without the brand name's full screen logo enabled in the bios don't be alarmed. You manually have to set the dram timings in the bios in order to see the full 800mhz displayed.

If there are no faults with the memory or cpu that would be the first item to look into there. Don't set the 1T/2T option to 1T however. Leave that at auto or 2T otherwise you have to clear the cmos in order to see the system bootup.