I’ve been using Dataram’s excellent free ramdisk program for several months now and highly recommend it. On some machines, I install Firefox to the ramdisk and move the profile there. But the biggest benefit comes from putting the profile (not just the browser cache) in the ramdisk. Storing the profile in a high-speed, near-zero-latency ramdisk solves virtually every Firefox performance issue.
When creating a ramdisk, you really want to make sure you leave at least 1 GB of memory for the system, and 2 GB is better. On a 32-bit system, I wouldn’t create more than a 1 GB disk–unless you have a 32-bit system with more than 4 GB of RAM in it. Dataram can use the otherwise inaccessible memory above 4 GB. And of course, on a 64-bit system with 8 GB or more, you can get away with making bigger ones. I always use Dataram’s setting to save the disk contents at shutdown and reload them at startup. That way I don’t lose my browser cache, history, or anything else. The benefit is almost as good as having a nonvolatile ramdisk would be.
To move the profile, first you have to find it. Once you find your profile, copy it to the ramdisk.
Next, close Firefox and launch Task Manager (the quickest way is to hit shift-ctrl-Esc), go to the Processes tab, and make sure Firefox.exe isn’t there. If it is, select it and click End Process.
Launch Firefox’s profile manager. The easiest way is to go to Start, Run, and type c:\Program Files\Mozilla Firefox\firefox.exe -profilemanager and click OK.
Click Create Profile. It will ask for a name. I name mine ramdisk. Click Choose Folder, then navigate to the folder you copied to your ramdisk and click OK. Then click Finish.
Select your ramdisk profile, then click Start Firefox.