Tkisem is "an instructional emulator for version 8 of the SPARC instruction set with a GUI based on Tcl/Tk." It seems to be mostly complete, but not quite as robust as QEMU. However, it may be a better starting point for learning Sparc Assembly language. It does have a non-standard MMU implementation.
To run the simulator, you need to have TCL 8.0 and TK installed. If you see missing library problems on Linux, just create a symlink from the the current version to the version Tkisem is looking for.
Windows and Linux both support tkisem; Linux additionally provides gxisem, which has a X11 interface.
There are installation instructions and lab manuals along with binaries in the distribution.
If you install TKisem on Windows, you may have trouble running as and ld. If you get a stack fault, try running the commands as-isem and ld-isem instead of isem-as and isem-ld. Also don't forget to add the programs to your PATH.