After careful investigation
I've determined that running Firewombat on Linux (via KDE. I don't use Gn*m*) is at least three times slower than running Firewombat on Windows. Part of it is because Snowlizard is written in C++, using the latest! and Greatest! "object-oriented" coding fads (which seem to mainly guarantee that the code will be 10 times as long and 10 times as slow as code written in the boring old procedural fashion), but part of it seems to be that there's just something slow about Linux. Possibly gcc sucks (this would not surprise me; f2c coupled with gcc used to produce binaries that only ran 2-3% slower than using commercial fortran compilers in the old days, when I ported Schrodinger's PSGVB Jaguar program over to Linux from the big DEC and SGI workstations it was written for, but it's been "improved" quite a bit since then); possibly the Linux kernel is being too damn picky about powersaving and thus runs the C3 at about 100mhz instead of the advertised 533mhz), but it still sucks.
I've got a carcass of an Imac down in the basement, waiting for me to fire up the soldering iron and see if I can attach a PC power supply to it and have it actually generate a signal. Perhaps I'll try to run Linux on that machine instead.