Absolutely PERFECT running under OS X 10.6.4!
That Apple does not offer this capability bewilders me.
This is far far better than using a terminal script that will create a Ram Disk:
Buried in the manual pages for Apple's command-line disk-image-management utility "hdid" are a few instructions on how to use this command to create and mount a RAM disk. The process basically involves creating a mount point for the disk, using the hdid command to allocate the RAM for the disk, and then create a file system on the disk so it can be used and mount it to the mount point.
mydev=`hdid -nomount ram://$NUMSECTORS`
mount -t hfs $mydev /tmp/mymount
Copy this text to a plain text document (not rich text) in TextEdit, and save it with ".sh" as the filename suffix (i.e., "ramdisk.sh"). Then open the Terminal and type "chmod u+x " followed by a single space, drag the script file to the Terminal window, and press enter. This will enable execution of the script by the owner of the file (you).
After this is done, to run the script just open a Terminal window, drag the script to it, and press enter. The default value for "NUMSECTORS" in the script will give you a 64MB RAM disk, but you can increase this number if you would like. The number represents sectors, and there are 512 bytes per sector of RAM. To edit the script after it has the .sh filename suffix, right-click it and choose TextEdit under the "Open With..." menu.
You can also run a similar script in one line using Apple's "diskutil" and "hdiutil" commands, which result in a more user-friendly RAM disk than the previous script.
diskutil erasevolume HFS+ "ramdisk" `hdiutil attach -nomount ram://128000`
When run in the Terminal, this command does a number of things (note the single quotes are actually "grave accent" marks). First it invokes "hdiutil" to attach an allotment of RAM but not yet mount it since there is no filesystem on it yet. After the RAM is allotted, it calls on the "diskutil" command to format the allotted RAM and name it "ramdisk," which will cause the Finder to mount it under that name in the default mount point /Volumes/.
This may be a preferred method because it is simpler and allows you to name the disk by changing the "ramdisk" name in the Finder.