It's not strange, all CPU is different, I had tested about 10 celeron 566 and the result is different, I had 2 run 850 @ 1.95 volt and the lowest run 1.6 @ 850, this CPU from different batch, the later the batch the better CPU. The other work 850 with different voltage most of them is 1.7 volt
The 1.95 v CPU from week 19 and the 1.6 CPU froom week 34.
If you guys can get the latest 633 with cC0 stepping you can get around 1 GHz easily, it's already in the market.
The reason I could get so many CPU to test cos I work at computer company.
2 volt is crazy? I don't think so if you have good cooling. Actually I run one CPU @ 2 volt for quite a long time, few months for sure since the first 566 hit the street and work fine until now. REMEMBER good cooling!!!