The reason is that Firefox tend to stay at 60-100% CPU for long periods, this seems to be something with javascript - sometimes I can stop the CPU hogging by leaving some Google sites, for example.
But with that extra core Firefox can have its own core. And I get to use the other. Now, I'm not sure if that's what multiple cores were meant for. It helps though..
Definitely sounds like scripttardery in action, and it being on Google sites is just confirmation of how Google has been wetting their own bed by doing all the things that originally killed off their competition. It's almost like they WANT to be the new "ask jeeves" at the WORST of the code bloat slow loading headache.
Certain scripting heavy sites, PARTICULARLY if you open multiple tabs can cause massive spikes -- MOST of them being social media. Google+, FaceBook, twitter and their kine are so massively and ridiculously scripting bound that REAL Opera (12, as opposed to the ridiculously dumbed down and useless ChrOpera), Firefox, and legacy versions of IE can end up so pathetically slow even on multicore the browser will flip in and out of "not responding" nonstop.
It's not as bad in Chrome and ChrOpera because every tab gets it's own process and thread and the V8 engine runs each sites scripting in another thread... and now has a JIT compiler in the mix. (which is why node-webkit is ALMOST viable for native app development) You may want to give chrome a try for sites having such issues, even if the user interface is dumbed down to the worst of IE 3 Quackintosh circa 1996.
(You'd almost think they were using console game design thinking).
Websites universally are pulling these dumbass scripttard stunts due to mouth breathing idiotic "framework" bull like jQuery, bloated "I can haz intarnets" markup, and other bits of idiocy that piss all over sites usability and functionality -- just so they can have "gee ain't it neat" animooted BS and resulting in mind-numbingly dumbass things like using hundreds of K of markup and a megabyte or more scripting to deliver single k totals of plaintext.
It's some real freaking herpaderp right now when it comes to website code -- and moronic simpleton bull like jQuery, turdpress, bootcrap, blueprint, LESS, SASS, OOCSS, even HTML 5 are what's really at fault alongside people sleazing together websites with such tools who to be frank have no business making websites in the first damned place.
... which is why you typically need a multi-ghz multi-core processor with broadband to do move the same amount of CONTENT we were 20 years ago with 486's over Dialup... and why so many websites are less useful now than they were just a decade ago.
Just look at these forums -- where vBull is pissing out 320k+ of scripttardery, 100k of CSS in three separate files, and a batshit insane 182k of markup for the main forum index which barely has 18k of plaintext on it -- anywhere from five to eight times as much markup should have been used, ten times the scripting needed for what's being done, and two and a half times more CSS than ANY website actually needs.
Makes me want to dump most of todays ignorant fools with the giant monkey brass to call themselves "designers" in a shark tank. <drEvil>and yes, I made air quotes with my fingers... "lasers" --
on the sharks freaking heads. </drEvil>.
I'm not rocking 25mbps down and a mutl-ghz quad core for the performance of a P150 shotgunning 112k when all I want to do is read and post on forums or Joe forbid read an e-mail. THANKS SCRIPTTARDS! Basically, my disgust for the state of web development has blossomed from "Disgust to the point of nausea" into full blown projectile vomiting, as MOST of the sleazeball asshats making the software being deployed have no business writing software for anyone! From the dipshits who make WYSIWYGS, to the halfwits behind CMS systems like turdpress, to the scam artist book writers encouraging people to use fat bloated junk like jquery and bootcrap -- time to line the lot of them up in the chute and put them down with 8 gauge solids to the head
like they all had hoof and mouth.