there's a huge difference between crystal or powder. If it's powder I don't think 100 a day is going to do very much, you'd have to be on for a pretty long time. 100 crystal is fairly light, especially compared to what I've read some people are doing. I was doing 200 crystal a day, and I was fine for the first few days but as soon as I decided to up my dose to 200 every 16 hours instead of 24, I completely dehydrated and I was on my ass, head-splitting miserable for four straight days.
better you start low and work your way up, to be safe.