Processes fast up until 1GB of RAM usage, then slow

Memory usage seems like it is just a coincidence. Your real issue at least with Firefox stutter is CPU usage - I have seen that if you have multiple tabs in FF that are all consuming CPU or there is another app that is taking up CPU (VM etc) then FF will stutter.

I haven't found any solution to that apart from limiting CPU usage by running less CPU hogs at once.

 

Hmm all bets off - Symantec Antivirus! I had to reinstall OS X last time I tried installing our corporate copy in order to get on VPN. Try uninstalling it and see I guess.

Also : If Firefox up2date? I know there were some pretty bad memory bugs fixed recently. The other thing to check is that do you always have high CPU when the stutter occurs (I bet you do since you have 8GB RAM most of it free. There is no other reason for stutter than CPU usage, if your machine isn't swapping.)

 

If you want to improve your performance, uninstall Symantec immediately. You don't need any 3rd party antivirus app to keep your Mac malware-free. Macs are not immune to malware, but no true viruses exist in the wild that can run on Mac OS X, and there never have been any since it was released 10 years ago. You cannot infect your Mac simply by visiting a website, unzipping a file, opening an email attachment or joining a network. The only malware in the wild that can affect Mac OS X is a handful of trojans, which cannot infect your Mac unless you actively install them, and they can be easily avoided with some basic education, common sense and care in what software you install. Also, Mac OS X Snow Leopard and Lion have anti-malware protection built in, further reducing the need for 3rd party antivirus apps.

Mac Virus/Malware FAQ​

If you're forced to use AV, use ClamXav. It is one of the best choices, since it isn't a resource hog, detects both Mac and Windows malware and doesn't run with elevated privileges. You can run scans when you choose, rather than leaving it running all the time, slowing your system. ClamXav has a Sentry feature which, if enabled, will use significant system resources to constantly scan. Disable the Sentry feature. You don't need it. Also, when you first install ClamXav, as with many antivirus apps, it may perform an initial full system scan, which will consume resources. Once the initial scan is complete, periodic on-demand scans will have much lower demands on resources.

No, because there's no magic "choke at 1GB" issue. You're misreading the symptoms. Your system will not choke because of 1GB of RAM usage. Not ever. There are other factors at work. Launch Activity Monitor and change "My Processes" at the top to "All Processes", then click on the CPU column heading once or twice, so the arrow points downward (highest values on top). Then look to see what may be consuming system resources.

 

Did you even read his actual post? He said uninstalling Norton is not an option since it is a company computer, not his personal computer.

 

Did you even read all of my post? Yes, I read all of the OP, and the post I responded to about uninstalling hadn't yet mentioned the work computer. Norton can be disabled without uninstalling it, and ClamXav can be used instead.

 

Thats his post directly above your post, that specifically states and I quote again "Unfortunately uninstalling AV is the one option I don't have, since this is a work machine."

So Yes I read your post, and his post, and the reply to my post that you made. Just posting links about information isn't appropriate in every circumstance but Ive noticed thats the thing you like to do in posts.