Seems to be some mis-information concerning this issue, so I'll set things straight ;-)
The JPEG decoder can be set to use a user defined amount of memory - if the decoder needs more, it is then that it uses the swap space. So, the whole point of this is that JPEGTMP: should be assigned to a physical disk and not a ram disk. If you want the decoder to use more ram (in particular, decoding progressive JPEGs requires much more ram than standard JPEGS), then there's usually an envvar to set that - I can't remember the name, but...
In the IBrowse image settings, you can change the swap space location (defaults to JPEGTMP:, IIRC). And if you prefer for IBrowse not to use the swap dir ever, then move the memory limit slider so that it shows "No limit". Technically, this has the same effect as setting swap to ram:, but this is a much more efficient way to do it (will use less ram, and is faster, since the libjpeg backing store functions aren't used anymore).
