150MHz. System requirements are, of course, 233MHz, but I gave both NS6 and NS7 a shot when they each came out. And both were too slow to be useful. When I saw NS7 Streamline, I really didn't expect it to work either, but I figured I'd try it. Like I said, it's still a bit slow, but I can live with it.
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The truth is, all might be free if they valued freedom, and defended it as they ought.