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This doesn't come anywhere close to 1900MH/s, so it seems there's a lot of hashrate that is missing.
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Actually, from my understanding, the hash-rate is determined using difficulty, and time to find a a block. So its not directly taken from whatever is connected and what they are reporting.
So it will take a day or two for the difficulty to adjust and then hash-rate will be known.
Interesting explanation, and not something I've heard before. I'm not saying I disagree with it - because I don't really know, frankly - but when Monero forked there was a sudden - near vertical - drop in hashrate; difficulty, however, took another day or so to adjust downward.