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June 07, 2013, 03:25:49 PM |
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The difficulty determines how fast blocks are mined and therefore how many orphans there are. Low diff = easy to find blocks = large chance of orphans.
The target block time is the desired average time between blocks. The difficulty has to be readjusted periodically to ensure that the actual time between blocks matches the target time. Network hashrate goes up -> difficulty goes up at the next readjustment.
In a stable situation (constant hashrate), a coin with a 5 second target block time will have a difficulty 60 times lower than a coin with a 5 minute target block time if both coins have the same network hashrate. Superfast coins will always have orphans, because they are designed to have blocks generated very quickly.
If the difficulty does not match the target block time, the time for transactions to confirm will also change. A coin that requires 6 confirms and has a 1 min target block time should normally confirm in ~6 minutes. If the network hashrate now drops by 50%, blocks will trickle in at half the pace, so getting those 6 confirms will take ~12 minutes on average. That is, until the next difficulty readjustment. Here also lies the problem with slowly adjusting coins: If the network hashrate drops a lot (which is common for altcoins as the large miners switch to the newest coin), it can take a very long time before the difficulty is adjusted downward, since readjustment-periods are typically specified in block-counts rather than in time-periods.
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