I have a Costa Rica 1.6a from Googlegear. I haven't been able to really hit 2.1ghz with that chip. The computer acts really funny at that speed, and I'm not sure if its a cpu limitation or a motherboard glitch. At anything over 125fsb the computer runs slow as hell. There are no blue screens, and the computer will eventually do the tasks you want. At those speeds though, it takes about 10 minutes to load windows 2000. That is the slowness I'm talking about.
I have another 1.6a sitting at home that just arrived. I'm hoping that it is a malay and will allow for higher overclocks, but we'll see.
BTW, I ordered the Samsung 8 device 256meg rimms from googlegear. They can't run even at a 125fsb. I have to lower the multiplier to push the cpu farther. I have 16 device rimms on the way. Hoping that will allow higher overclocking of the memory.