Well, I own a Duron 850 myself, but I'm on SDR, not DDR. The FSB is 100Mhz, therefore 9x100. You can usually clock the FSB up to 133Mhz, I'm running my 850 @ 1066 (approx 8 x 133)Mhz. It doesn't really get that warm, but loses stability once you go over 1100 Mhz. I'm not sure which type of DDR ram you would need, I would think that it would be dependant on the Motherboard, the manual should note what type of DDR rame would work best.