Dave, just to clarify a little bit.
SPARC is a hardware platform provided by the group 'Sun Microsystems'. It's a RISC based processor system.
From distribution, they usually run Solaris, but they can also run Linux (and there are many very happy Sun boys and girls running Linux on their little sparkies).
A paralell can be drawn between Sun and HP in this reguard. IE: PA-RISC systems are distributed by HP with HPUX on them. Unfortunately, Linux for PA-RISC is only under development from what I've heard however *pout*.
One long-haired git at your service...