Check VRM temps. When load varies like that it could be thermal throttling due to overheating VRM.
A utility like GPU-Z will show you VRM temps. Note something which only shows a single temp isn't useful. There are 8 different temps on each graphics card (12 if you have dual GPU card). The VRM temp (called VDDC in GPU-Z is the one to look at.
Topic: Hash rate swinging a lot (Read 1505 times)
using guiminer opencl, temperature looks fine, it's 78-80 max on 5850 and below 70 max on 5870
Could still be wrong though 
In GUIminer, What flags do you use?
using guiminer opencl, temperature looks fine, it's 78-80 max on 5850 and below 70 max on 5870
what miner are you using? What is the temperature like on the cards?
I mean i have an elitexstream 800w powering 3x 5850 just fine on my other rig
I don't think it's the power supply unless it's faulty. I have a hx850 powering a 5870 and a 5850 with an amd sempron + 1gb ddr3 ram stick
Might be a weak power supply. What are the specs (all of them) for your rig?
Hey guys, I have two miners where the hash rates stay mostly constant but on one miner the hash rate changes a lot. Gpu utilization keeps going from like 99% to like 80% and all the way in between.
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