I am running these on gentoo with cgminer 2.11.3 (I've tried 2.10.4 as well), and I noticed that the MH/s for each card initially goes up to 505/526 for the first minute or two. Over the next 3-5 minutes it settles into 480/490 MH/s. In the first period the gpu load is 98-100%, but as it declines and once it hits steady state the gpu load alternates between 64% and 98-100%. I have tried altering the intensity (8, 9, 10), the worksize (256, 512, 1024), the # of gpu threads (1, 2, 3), and the queue size (1,3,5), and the kernel (diakgcn, diablo, poclbm). All of these settings give the same behavior (though the starting and steady state hashing speeds differ slightly). I do not see this behavior on my boxes with 2x5830s, 2x5770s, or 1x7950 & 1x5770. Any thoughts as to what might be causing this or some other test I can try?