With pc2100 ram can run at 266mhz, so you could go to a 133fsb without overclocking the ram. That would put your 1.8a at just under 2.4Ghz. 1.8a's tend to be good overclockers, like the 1.6a. I have 2 1.6a's running at 2.1ghz(133fsb) and they are no warmer than at stock speed, and are using the intel heat sink and fan.