Sorry, no, what I should have said is that in normal use, CPU load is very low, but it occasionally ramps up to around 35% for about 30 seconds. After a while, these continual bumps cause the temperature to steadily rise to the point that the left hand underside gets very hot and the fans run a lot. This is compared with how it used to run under Panther, where I could use it for much longer periods without it getting any where near as hot as it does now.
I'll try to post some screen shots later to illustrate, as that might make it clear
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