I understand fluctuations in WU and reject rate when starting out a fresh run of cgminer, but what Im talking about is fluctuations in hashrate appearing after running for 24 hrs. For example on a fresh run my 7950s get stable as a rock 640khs, but when I check them at the end of the day they are fluctuating between 590-635 constantly, I also thought I may be because of coin/difficulty changes, but the fluctuations continue even during a specific coin. One strange thing is that one of the cards doesn't seem to fluctuate at all and stays at 640, btw the rig Im talking about has 6 - 7950's in it, running Windows 7 headless. And all this fluctuation immediately stops when I restart cgminer.
It's pretty simple. Your rig isn't as stable as you think it is. You need to tweak your settings to see what's going on. I bet you're seeing GPU usage % is fluctuating too.
You likely have one or more of the following going:
-interference between cgminer and a memory intensive CPU miner (PTS for example)
-your clock/voltage settings of one or more of your video cards is not recovering properly following a driver crash
-your OC isn't stable causing the driver crash in the first place
-your PSU is underpowered for the power requirements.
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Next thought. Can everyone please stop referring to WU in terms of MH/s. WU is not measured in MH/s, it's measured in shares/min.
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Next thought. It seems the useast server is having troubles. My miners keep failing over to the default west (middlecoin.com) server.