You can set the CPU:memory ratio. In the bios they do not show a ratio but you are able to select a speed. The speed shown is calculated using a ratio. When you change the FSB the memory frequancy will change too acording to the speed you have selected.
In the bios if you go into "Frequency/Voltage Control" you will the "DRAM Frequency" selection. With a 800mhz CPU you have the choise of "266, 333, 400, auto, 500, 532".
I have chosen 333 which has a 5/6 (166/200) multiplier. When I change the CPU core speed from 200 to 250, it gives me a memery speed of memory speed of 208.3mhz (5/6 x 250).
When I left the memory speed at "400" or "auto" I couldn't make it past 210mhz.
Have you guys tried selecting "266" already? Acording to my thoery you would get the 2/3 ratio you are after.
RideGuy