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Also, LTC mining requires more power due to increased VMEM usage. You must have pushed the PSU to it's limits.
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So that is most likely the reason for your PSU failure
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https://bitcointalksearch.org/topic/--91156
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I played with worksize and aggression. Touching those setting usually optimize. I can't get the card to even start with reaper without a crash.
The difference between 300 memory and 800+ does take a toll. I'm guessing my PSU was at it's limit already. That's not to say that Reaper could REALLY use an update for efficiency. I'm thinking we'll be seeing a lot of those types of questions in the next few months.