Firefox's use of CPU resources has improved but hasn't gone away completely.
I wrote about this last November after I had been grappling with this issue for more than a year. First, on an Hewlett-Packard business ultraportable and then on the Apple MacBook Air. As I stated at the time, my theory is that many users don't notice Firefox CPU utilization on large, well-ventilated mainstream laptops. But it can be an issue on ultraportables, which are more sensitive to heat because of the obvious design constraints (typically under an inch thick).
On the HP ultraportable (model 2510p, running Windows Vista), CPU usage became a major concern. The cause was twofold. First, at least one HP 2510p SKU (using a 1.33GHz CPU--the configuration I owned) had a design problem. When the unit got hot, it would shut off without warning. That, combined with Firefox's CPU usage issues, as spelled out clearly by Mozilla in the link above, made for an unstable mix. Firefox, I determined after much trial and error, triggered most of the shutdowns on my HP laptop.
While this never happened running Firefox on the MacBook Air (which I use now), it did continue to cause overheating. I have both the original MacBook Air (which uses an older 1.8GHz Intel Core 2 Duo processor) and a newer version (which has a newer 1.86GHz Core 2 Duo processor). Running Firefox on the older Air became unsustainable at times because of the heat issue. While moving to Safari didn't completely alleviate the heat problem, Safari did not generate the level of heat and fan activity that Firefox did.
Before I go any further describing the issue, let me say this: that was then. Mozilla has made strides--at least for the Web pages I access most often--in improving Firefox CPU utilization on the Mac.… Read more