If you are not using the visualization features in HSpot, then it may run acceptably on an Ultra 1 with 256 MB of RAM. HSpot will not run acceptably on Sparc 1, 2, 5, 10, or 20 workstations.
We have used HSpot extensively on a 32-bit Windows XP machine with 512MB RAM with good results.
We have done some testing on machines running 32-bit Java. However this has been less extensive than on Windows XP.
We have done limited testing on Linux systems running with a Pentium 2 processor at 266 MHz and 256 MB of RAM, as well as with a Pentium 3 processor and 256 MB of RAM.