Warning: serious geekery follows. Feel free to avoid if browser tech isn't your preferred recreation. 
I've been playing with Firefox 4.0 Beta12pre (a/k/a Minefield), on a Windows XP Pro SP3 box with 3GB RAM. (It has 4GB, but the BIOS only reports 3 to Windows. The 4th GB is apparently unusable. 
)
I've got it pretty well where I want it, and at this point, it's replaced FF 3.6.13 as my production browser.
One of the things I've been playing with is something I used to do in the old MS-DOS days. My old PC XT clone had 640K of main memory, and a card with a megabyte of add-on memory that could be utilized through software. So at bootup, I'd load a driver that configured 512KB of that add-on memory as a ramdisk, that looked and acted like a disk drive but was actually in RAM. My boot process would copy frequently used utilities to it, and add the ramdisk as the first entry in the PATH. MS-DOS and programs that created and used temp files were told to use the ramdisk for it. It sped things up a treat.
Ramdisk software exists for Windows, and since I have 3GB of RAM, I can afford to carve off a chunk as a ramdisk and fiddle. So I have a 256MB ramdisk seen by Windows as compressed NTFS volume Z:.
The first thing I tried was keeping Firefox's cache there. That's easy. Go into about
:config and create the new string preference browser.cache.disk.parent_directory. Set the value to the location you want the cache to be, which in this case is Z:\\. Poof! FF is using the ramdisk for cache. (On Linux I put cache in POSIX shared memory - /dev/shm - which exists in RAM or swap but not in the HD file system.)
Well, why stop there? Why not have the Firefox profile on the ramdisk? That's fairly easy, too. First, I copied the contents of my standard FF profile to the ramdisk. Next, I needed to get FF to use it. To do that, I created a new profile called "Ramdisk", and used Choose Folder in the Profile Manager to point to the folder on the ramdisk as the one to use. Poof! FF 4.0 was running, using the profile on the ramdisk.
Okay, so far so good. Now, can Firefox itself run from the ramdisk? Yes. I copied the directory in Program Files where Minefield is installed to the ramdisk, then navigated to it in Windows Explorer and executed Firefox.exe. It ran fine, and Sysinternals Filemon confirmed that all FF related disk I/O was to the ramdisk, not the hard drive.
So I created a shortcut on the desktop that runs FF 4.0 from the ramdisk, and tells it to use the ramdisk profile. Thus far, it's working fine, and it's probably about as fast as FF can get on the box.
It's still a work in progress. I'm in the middle of creating WinXP startup process that will create the proper directories and copy the needed files to the ramdisk when Windows is booted. The bigger issue is entries that will copy changed files
back to the hard drive on shutdown, so changes don't get lost if I have to reboot. It appears I can use gpedit.msc, the Group Policy Editor, to run a shutdown script. (This is only available in XP Pro. XP Home lacks it.) I will unavoidably lose stuff if I crash and must use the three-fingered salute to restart Windows, but I can live with that.)
Mostly, this is a "because I
can" exercise, and not something I recommend to general users, but it's been fun so far and FF run this way
is quick.
______
Dennis